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| Angle | The union of two co-planar rays intersecting at a common endpoint. |
| Center Line | A line consisting of a long dash followed by a short dash, that is used to show and locate centers of arcs and circles, and to describe the center axis of cylindrical forms. |
| Circle | A closed curve with coplanar points at the same distance from the center point. |
| Contour | An outline, especially of something curved or irregular. |
| Detail | Shape or feature on a model. |
| Diagonal | A line that is slanting or oblique. |
| Dimension | Numerical value used on a drawing to describe location, size, shape, or geometric characteristic. |
| Dimension Line | Thin line segment capped on the ends with arrowheads, that indicate the length of the dimension. |
| Dimensioning | The process of placing measurements and notes on a drawing to completely communicate its meaning. |
| Edge | The line where two surfaces or points intersect. |
| Ellipse | The group or set of all points in the same plane whose sum of distances from two points (foci) is constant. An ellipse looks like a squashed circle or a circle viewed at an angle. |
| Essence | The quality or nature of something that identifies it or makes it what it is. |
| Extension Line | Thin lines used to establish the extent of a dimension. |
| Feature | Any physical portion of an object, such as a hole or fillet. |
| Freehand | Done without the use of tools or drawing equipment. |
| Ground Line | In a perspective drawing, the plane where objects appear to rest. |
| Horizon Line | In a perspective drawing, the imaginary line at eye level used as a construction line. |
| Horizontal | A line parallel to the horizon. |
| Isometric | A drawing projected so that the plane of projection of a three-dimensional drawing forms equal angles (120 degrees) to each of the three axes of the object. |
| Line | The path of an infinite series of points. A line has length, but not width or thickness. |
| Line Segment | A portion of a line that is defined by two points. |
| Line Weight | The width and darkness of a line. |
| Mass | The quantity of matter, which a material contains. |
| Object | Something visible or tangible. |
| Object Line | Slightly lighter than a profile line, used to add all details to a sketch. |
| Oblique | A form of pictorial sketch in which two axes are at right angles to each other (one vertical, one horizontal) and the depth axis is at an oblique angle. |
| Order of Views | The relationship between the views in orthographic projection. |
| Orthographic | Right angle projection. The views of an object are drawn in perpendicular planes to one another. |
| Pattern | A regular or repeated design, form, order, or arrangement. Duplicates one or more components and arranges the resulting occurrences in a circular or rectangular pattern. |
| Picture Plane | In a perspective drawing, it is the plane of projection. |
| Profile Line | In sketching, a dark heavy line that outlines the object drawn. |
| Projection Plane | An imaginary plane in the line of sight on which an image appears. |
| Proportion | Proportion is a Principle of Design. Comparative relationship between things with respect to size. |
| Scale | A graduated series of numbers used for measurement purposes. |
| Shape | The physical geometry of a model. |
| Sketch | A freehand drawing of an idea, or solution to a problem without concern for detail. |
| Station Point | The point where the viewer stands to observe the image on the picture plane. |
| Surface | A two-dimensional area on a plane. |
| Vanishing Point | The point on the horizon where parallel objects appear to intersect due to convergence. |
| Vertical | Perpendicular to the horizon. |
| Views | The different viewing perspectives found in mechanical drawing. |
| Visualization | To form a mental image of something. |
