Art Definitions, Glossary of Terms

Freehand Drawing Book

DEFINITIONS.

Aesthetics. The science which treats of the beautiful, and its various modes of representation in Nature and art ; the philosophy of the fine arts.

Accent. Emphasis of light or of dark in a light-and-shade drawing ; of dark in an outline drawing ; and of color or of light and dark in a color sketch.

Altitude. The perpendicular distance between the bases, or between the vertex and the base, of a solid or plane figure.

Angle. The difference in direction of two lines which meet or tend to meet. The lines are called the sides, and the point of meeting, the vertex of the angle.
An angle is measured by means of an arc of a circle described from its vertex as a centre and included between its sides. The centre of the arc is the vertex of the angle.
If the radius of the circle moves through     of the circumference,
it produces an angle which is taken as the unit for measuring angles, and is called a degree.
The degree is divided into sixty equal parts called minutes, and the minutes into sixty equal parts called seconds.
Degrees, minutes, and seconds are denoted by symbols. Thus 5 degrees, 13 minutes, 12 seconds, is written 5° 13' 12".

A RIGHT ANGLE is one which is formed by the radius moving through 1/4 of the circumference. It is an angle of 9o°. A straight angle is formed when the radius has moved over 1/2 of the circumference. It is an angle of 180°.
ACUTE ANGLE. An angle less than a right angle.
OBTUSE ANGLE. An angle greater than a right angle.
OBLIQUE ANGLE. One which is not a right or a straight angle.
REFLEX ANGLE. One which is greater than 180°.
ADJACENT ANGLE. Two angles are adjacent when they have the same vertex and a common side.
DIHEDRAL ANGLE. The opening between two intersecting planes.
SOLID ANGLE. One formed by planes which meet at a point.

Apex. The summit or highest point of an object.

Appearance. The image produced in the eye by the outline, light and shade, or color of any object.

Arc. See Circle.

Arrangement. The orderly disposition of objects or forms.

Axis of a Solid. An imaginary straight line passing through its centre and about which the different parts are symmetrically arranged.

Axis of a Figure. A straight line passing through the centre of a figure, and dividing it into two equal parts.

Axis of Symmetry. A straight line so placed in a solid or a plane figure that every straight line meeting it at right angles and extending in each direction to the boundary of the solid or figure is bisected at the point of meeting. In many solids and plane figures an axis of symmetry cannot be drawn.

Balance. The equality of parts, obtained by the proper distribution of lines or of light and dark.

Base. The opposite parallel polygons of prisms. The polygon opposite the vertex of a pyramid. The plane surfaces of cylinders and cones. The opposite parallel sides of a parallelogram or trapezoid. The shortest or longest side of an isosceles triangle, and any side in any other triangle, but usually the lowest.

Bisect. To divide into two equal parts.

Bisector. A line which bisects.

Bisymmetrical. Having one side the exact reverse of the other side. Blend. To soften and bring together.

Blocking-in Lines. The lightest and simplest suggestions of the leading lines and masses of the subject.

Border. Ornament, usually composed of units regularly repeated along a line.

Breadth. Simplicity due to large masses which subordinate details to the spirit and effect of the whole.

Chiaro-oscuro. The art of combining light and shade.

Cinquefoil. A figure composed of five leaf-like parts.

Circle. A plane figure bounded by a curved line, called a circumference, all points of which are equally distant from a a point within called the centre.

The boundary line is called the CIRCUMFERENCE.
DIAMETER. A straight line drawn through the centre, and connecting opposite points in the circumference, as a b.
RADIUS. The distance from its centre to the circumference, as c e.
SEMI-CIRCLE. Half a circle, formed by bisecting it with a diameter, as a db a.
ARC. Any part of the circumference, as e b.
CHORD. A straight line whose ends are in the circumference, as fg..
SEGMENT. The part of a circle bounded by an arc and a chord, as f h g f.
SECTOR. The part of a circle bounded by two radii and an arc, as b e c b.
QUADRANT. A sector bounded by two radii and one fourth of the circumference, as a c d a.
TANGENT. A straight line which meets a circumference, but being produced does not cut it, as k d. The point of meeting is called the point of contact or point of tangency.

Circumscribe. A polygon is said to be circumscribed about a circle when each side of the polygon is a tangent to the circle ; and a circle is said to be circumscribed about a polygon when the circumference of the circle passes through all the vertices of the polygon.

Color. For color terms, see Color Manual.

Concave. Curving inwardly.

Cone. A solid bounded by a plane surface called the base, which is a circle, ellipse, or other curved figure, and by a lateral surface which is everywhere curved, and tapers to a point called the vertex. Its base names the cone. Thus a circular cone is one whose base is a circle.
A RIGHT CIRCULAR CONE is generated by an isosceles triangle which revolves about its altitude as an axis. The equal sides or the triangle in any position are called elements of the surface. The length of an element is called the slant height of the cone. Unless otherwise stated " cone " means a right circular cone.
A FRUSTUM OF A CONE is the part included between the base and a plane parallel to the base and cutting all the elements of the cone.
A TRUNCATED CONE is the part included between the base and a plane oblique to the base and cutting all the elements of the cone.

Concentric. Having a common Centrex.

Conic Section. A section obtained by cutting a cone by a plane.

Construction. The making of any object.

Construction Lines. The lines by which the desired result is obtained.

Constructive Drawing. A drawing intended for the workman who is to make the object.

Contour. The outline of the general appearance of an object.

Contour Element. An element which is in the contour of an object.

Contrast. The effect due to the juxtaposition of different lines, different forms, different masses of light and dark, or different colors.

Conventionalization. In art, the expression of the spirit and important truths of Nature by a subordination of less important features.

Convergence. Lines extending toward a common point, or planes extending toward a common line.

Convex. Rising or swelling into a spherical or rounded form.

Corner. The point of meeting of the edges of a solid, or of two sides of a plane figure.

Crescent. A figure.of the shape of the new moon.

Cross. Two bars, or parts, intersecting or crossing each other in various ways. The symbol of the Christian religion.

Cross-hatched. In mechanical drawing, a half tinting placed upon parts cut by a cutting plane. In free-hand drawing, the use of lines crossing each other and producing light and shade effects.

Curvature. Variation from straightness.

Curve. A line of which no part is straight.

REVERSED. One whose curvature is first in one direction and then in the opposite direction.
SPIRAL. A plane curve which winds about and recedes, according to some law, from its point of beginning, which is called its centre.

Cylinder. A solid bounded by a curved surface and- by two opposite faces called bases ; the bases may be ellipses, circles, or other curved figures, and name the cylinder. Thus a circular cylinder (the ordinary form) is one whose bases are circles.

A RIGHT CIRCULAR CYLINDER is generated by the revolution of a rectangle about one side as an axis. The side about which the rectangle revolves is called the height of the cylinder, also its axis. The side opposite the axis describes the curved surface of the cylinder, and in any of its positions is called an element of the surface.

Cylindrical. Having the general form of a cylinder.

Degree. The 36oth part of a circumference of a circle. Describe. To make or draw a curved line.

Design. Any arrangement or combination to produce desired results in industry or art.

Develop. To unroll or lay out upon one plane the surface of an object

Diagonal. A straight line in any polygon which connects vertices not adjacent.
In regular polygons, diagonals are called long when they pass through the centre, as c d, and short when they extend between parallel sides as a b.

Diameter. See Circle. In a regular polygon with an even number of sides a line joining the centres of two opposite sides is often called a diameter.

Diverging Lines. Lines extending from a common point.

Edge. The intersection of any two surfaces. The boundary line. Edges are straight or curved, and are represented by lines.

Elevation. A drawing made on a vertical plane by means of projecting lines perpendicular to the plane from the points of the object. The terms elevation, vertical projection, and front view all have the same meaning.

Ellipse. A plane figure bounded by a line such that the sum of the distances of any point in it, as c, from two given points e and f, called foci, is equal to a given line, as a b. The point midway between the foci is called the centre.
The TRANSVERSE Axis of an ellipse is the longest diameter that can be drawn in it, as a b. It is also called the major or long axis.
The CONJUGATE Axis is the shortest diameter which can be drawn, as c d. It is also called the minor or short axis. The foci, e and f, are two points in the long diameter whose distance from c or d is equal to one-half a b.

Face. One of the plane surfaces of a solid. It may be bounded by straight or curved edges.

Finishing. Completing a drawing, whose lines have been determined, by erasing unnecessary lines and strengthening and accenting where this is required.

Foreshortening. Apparent decrease in length, due to a position oblique (or parallel) to the visual rays.

Free Arm Movement. Movement of the arm from the shoulder.

Free-hand. Executed by the hand, without the aid of instruments.

Fret. A band or border composed of lines forming a succession of angles and often interlacing.

Frustum. See Cone and Pyramid.

Generated. Produced by.

Geometric. According to geometry.

Gradation. A gradual change from light to dark, or from one color to another.

Half-tint. The shading produced by means of parallel equidistant lines.

Hemisphere. Half a sphere, obtained by bisecting a sphere by a plane.

Horizon. In pictorial art, a horizontal line at the level of the eye.

Horizontal. Parallel to the surface of smooth water.
In drawings, a line parallel to the top and bottom of the sheet is called horizontal.

Inscribe. A polygon is said to be inscribed in a circle when all its vertices are in the circumference of the circle ; and a circle is said to be inscribed in a polygon when the circumference of the circle is touched by each side of the polygon.

Instrumental. By the use of instruments.

Interlacing. The arrangement of one part of a design so that it passes alternately above and below another part.

Lateral Surface. The surface of a solid excluding the base or bases.

Level of the Eye. The level or position of a horizontal plane passing through the spectator's eye.

Line. A line has length only. In a drawing its representation has width but is called a line.

STRAIGHT. One which has the same direction throughout its entire length.
CURVED. One no part of which is straight.
BROKEN. One composed of different successive straight lines.
MIXED. One composed of straight and curved lines. CENTRE. A line used to indicate the centre of an object.
CONSTRUCTION. A working line used to obtain required lines.
DOTTED. A line composed of short dashes.
DASH. A line composed of long dashes.
DOT and DASH. A line composed of dots and dashes alternating.
DIMENSION. A line upon which a dimension is placed.
FULL. An unbroken line, usually representing a visible edge.
SHADOW. A line about twice as wide as the ordinary full line.
A straight line is often called simply a line, and a curved line, a curve.

Longitudinal. In the direction of the length of an object.

Model. A form used for study.

Oblique. Neither horizontal nor vertical.

Oblong. A rectangle with unequal sides.

Ornament. Decorative arrangement of line, light and shade, color, or relief.
HISTORIC. That designed in previous ages.

Oval. A plane figure resembling the longitudinal section of egg ; or elliptical in shape.

Overall. The entire length.

Ovoid. An egg-shaped solid.

Parallel. Having the same direction and everywhere equally distant.

Parallelogram. See Quadrilateral.

Pattern. That which is used as a guide or copy in making anything. FLAT. One made of paper or other thin material..
SOLID. One which reproduces the form and size of the object to be made.

Perimeter. The boundary of a closed plane figure.

Perpendicular. At an angle of 90°.

Perspective. The art of making upon a plane, called the picture plane, such a representation of objects that the lines of the drawing appear to ' coincide with those of the object, when the eye is at one fixed point called the station point.
DIAGRAM. An exact perspective drawing obtained scientifically by perspective methods. It is often very fals5 pictorially when not seen from the station point.
PARALLEL. Diagram perspective which represents a cubical form by the use of one vanishing point, and represents by its real shape any face parallel to the picture plane.
ANGULAR. Diagram perspective in which two sets of horizontal edges of a cubical form are at angles to the picture plane, and the object is thus represented by the use of two vanishing points.
OBLIQUE. Diagram perspective in which, none of the edges of a cubical form being parallel to the picture plane, it is represented by the use of three vanishing points.
FREE-HAND or MODEL DRAWING. A drawing which, without confining the eye to the station point, represents as far as possible the actual appearance of objects. It is made free-hand, and is for most purposes more satisfactory than an exact diagram perspective.

Plan. Plan, horizontal projection, and top view have the same meaning, and designate the representation of an object made on a horizontal plane by means of vertical projecting lines. In architecture it means a horizontal section.

Plane Figure. A part of a plane surface bounded by lines.
A plane figure is called rectilinear if bounded by straight lines, curvilinear if bounded by curved lines, and mixtilinear if bounded by both straight and curved lines.
Similar figures are those that have the same shape.

Plinth. A cylinder or prism, whose axis is its least dimension. It is circular, triangular, square, etc., according as it has circles, triangles, squares, etc., for bases.

Polygon. A plane figure bounded by straight lines.
An EQUILATERAL POLYGON is one whose sides are all equal.
An EQUIANGULAR POLYGON is one whose angles are all equal.
A REGULAR POLYGON is one which is equilateral and equiangular.
PARALLEL POLYGONS are those whose sides are respectively parallel.

TRIANGLE. A polygon having three sides (1).
QUADRILATERAL. A polygon having four sides (2).
PENTAGON. A polygon having five sides (3).
HEXAGON. A polygon having six sides (4).
HEPTAGON. A polygon having seven sides (5).

OCTAGON. A polygon having eight sides (6).
NONAGON. A polygon having nine sides (7).
DECAGON. A polygon having ten sides (8).
UNDECAGON. A polygon having eleven sides (9).
DODECAGON. A polygon having twelve sides (to).
The centre of a regular polygon is the common intersection of perpendiculars erected at the middle points of its sides.
The polygons represented in the figures are regular polygons.
A Polyhedron is a solid bounded by planes. It is regular when its faces are regular equal polygons.
There can be but five regular polyhedrons :
I. The TETRAHEDRON, or PYRAMID, which has four triangular faces.
2. The HEXAHEDRON, or CUBE, which has six square faces.
3. The OCTAHEDRON, which has eight triangular faces.
4. The DODECAHEDRON, which has twelve pentagonal faces.
5. The ICOSAHEDRON, which has twenty triangular faces.
The term hexahedron is applied only to a regular polyhedron : the other terms may be applied to irregular polyhedrons.
An infinite number of irregular polyhedrons, also an infinite number of other solids bounded by plane or curved surfaces, may be conceived.

Prism. A solid bounded by two equal parallel polygons, having their equal sides parallel, and by three or more parallelograms.
The polygons are called the bases of the prism, the parallelograms the lateral faces, the intersections of the lateral faces, the lateral edges.

Prisms are called triangular, square, pentagonal, etc., according as the bases are triangles, squares, pentagons, etc.
A RIGHT PRISM is one in which the edges connecting the bases are perpendicular to the bases.
An OBLIQUE PRISM is one in which the edges connecting the bases are not perpendicular to the bases.
A REGULAR PRISM is a right prism whose bases are regular polygons.
A TRUNCATED PRISM is the part of a prism included between the base and a section made by a plane inclined to the base, and cutting all the lateral edges.

Produce. To continue or extend.

Profile. The contour outline of an object.

Projection. Orthographic. The view or representation of an object obtained upon a plane by projecting lines perpendicular to the plane.

Pyramid. A solid of which one face, called the base, is a polygon, and the other faces, called lateral faces, are triangles having a common vertex called the vertex of the pyramid. The intersections of the lateral faces are called the lateral edges.
A pyramid is called triangular, square, etc., according as its base is a triangle, square, etc.
A REGULAR PYRAMID is one whose base is a regular polygon and whose vertex is in a perpendicular erected at the centre of the base. Its other faces are equal isosceles triangles. The altitude of any of these triangles is called the slant height of the pyramid. 111
A FRUSTUM of a pyramid is the part included between the base and a plane parallel to the base and cutting all the lateral edges.

A TRUNCATED PYRAMID is the part included between the base and a plane oblique to the base and cutting all the lateral edges.
The Axis of a pyramid is a straight line connecting the vertex and the centre of the base.
The ALTITUDE of a pyramid is the perpendicular distance from the vertex to the base.

Quadrant. See Circle.

Quadrilateral. A plane figure bounded by four straight lines. These lines are the sides. The angles formed by the lines are the angles, and the vertices of these angles are the vertices of the quadrilateral.

A PARALLELOGRAM is a quadrilateral which has its opposite sides parallel.
A TRAPEZIUM is a quadrilateral which has no two sides parallel.
A TRAPEZOID is a quadrilateral which has two sides, and only two sides, parallel.
A RECTANGLE is a quadrilateral whose angles are right angles.
A SQUARE is a rectangle whose sides are equal.
A RHOMBOID is a parallelogram whose angles are oblique angles.
A RHOMBUS is a rhomboid whose sides are equal.

Quadrisect. To divide into four equal parts.

Quatrefoil. A figure composed of four leaf-like parts.

Radiation. Proceeding from a common point or line.

Reflected Light. The light seen on the shadow side of any object, and reflected from some other object.

Relation. The harmony or contrast of form, value, or color. Rendering or Handling. The way in which a medium is used.

Repetition. The arrangement of a unit on a line, around a centre, about a line as axis, or upon geometric lines covering a surface.

Representation. Any kind of drawing, painting, or sculpture.

Retreating. Going away from.

Rosette. Arrangement of petal-like units about a centre.

Section. A projection upon a plane parallel to a cutting plane which intersects any object. The section generally represents the part behind the cutting plane, and represents the cut surfaces by cross-hatching.

Sectional. Showing the section made by a plane.

Sector and Segment. See Circle.

Shadow. Shade and shadow have about the same meaning, as generally used ; but it will be well to designate by shadow those parts of an object which are turned away from the direct rays of light, while those surfaces which receive less direct rays and are intermediate in value between the light and the shadow are called shade surfaces.
CAST. The shadow projected on any body or surface by some other body.

Similar Figures are those which have the same shape.

Solid. A solid has three dimensions, length, breadth, and thickness. It may be bounded by plane surfaces, by curved surfaces, or by both plane and curved surfaces. As commonly understood, a solid is a limited portion of space filled with matter, but geometry does not consider the matter and deals simply with the shapes and sizes of solids.

Sphere. A solid bounded by a curved surface every point of which is equally distant from a point within called the centre.
A sphere may be generated by the revolution of a circle about a diameter as an axis.

Spheroid (Ellipsoid). A solid generated by the revolution of an ellipse about either diameter. When revolved about the long diameter, the spheroid is called prolate or the long spheroid ; when about the short diameter, it is called oblate or the flat spheroid. • The earth is an oblate spheroid.

Spiral. See Curve.

Stippling,. Filling in the space between hatching lines, or producing an effect, by means of dots.

Surface. The boundary of a solid. It has but two dimensions, length and breadth.
Surfaces are plane or curved.
A PLANE SURFACE is one upon which a straight line can be drawn in any direction.
A CURVED SURFACE is one no part of which is plane.
The surface of the sphere is curved in every direction, while the curved surfaces of the cylinder and cone are straight in one direction.
The surface of a solid is no part of the solid, but is simply the boundary of the solid. It has two dimensions only, and any number of surfaces put together will give no thickness.

Symbolism. The use of conventional forms to suggest ideas not inherent in the forms.

Symmetry. Design. A proper adjustment or adaptation of parts to one another and to the whole.
BILATERAL. Having two parts in exact reverse of each other.

Symmetry. Geometry. If a solid can be divided by a plane into two parts such that every straight line, perpendicular to the plane and extending from the plane in each direction to the surface of the solid, is bisected by the plane, the solid is called a symmetrical solid, and the plane is called a plane of symmetry. If two planes of symmetry can be drawn in a solid, their intersection is called an axis of symmetry. See Axis of Symmetry.
The line about which a plane figure revolves when it generates a solid of revolution is an axis of symmetry for the solid ; it is also called the axis of revolution.
Tangent. A straight line and a curved line, or two curved lines, are tangent when they have one point common and cannot intersect ; lines or surfaces are tangent to curved surfaces when they have one point or one line common and cannot intersect.

Technique. The handling or way in which an effect is obtained.

Texture. The character of a surface.

Trefoil. A figure composed of three leaf-like parts.

Triangle. A plane figure bounded by three straight lines. These lines are called the sides. The angles that they form are called the angles of the triangle, and the vertices of these angles, the vertices of the triangle.
Triangles are named by their sides and angles.

A SCALENE TRIANGLE is one in which no two sides are equal.
An ISOSCELES TRIANGLE is one in which two sides are equal.
An EQUILATERAL TRIANGLE is one in which the three sides are equal.
A RIGHT TRIANGLE is one in which one of the angles is a right angle.
An OBTUSE TRIANGLE is one in which one of the angles is obtuse.
An ACUTE TRIANGLE is one in which all the angles are acute.

Trisect. To divide into three equal parts.

Truncated. A truncated solid is the part of a solid included between the base and a plane cutting the solid oblique to the base.

Type Form. A perfect geometrical plane figure or solid.

Unit of Design. The figure repeated in a design or arrangement.

Value. In color the relative amount of light contained in different colors. The strongest value is the lightest.
As used by artists the word generally means the difference in effect due to any cause whatever, as light, color, shadow, atmosphere, etc.
A flat value is one with no gradation.

Variety. The effect due to the combination of parts which are not alike.

Vertical. Upright or perpendicular to a horizontal plane or line. Vertical and perpendicular are not synonymous terms.

Vertex. See Angle, Quadrilateral, Triangle. The vertex of a solid is the point in which its axis intersects the lateral surface.

View. See Elevation. Views are called front, top, right or left side, back, or bottom, according as they are made on the different planes of projection. They are also sometimes named according to the part of the object shown, as edge view, end view, or face view.

Working Drawing. One which gives all the information necessary to enable the workman to construct the object.

Working Lines. See Lines.

The End.

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