JC Graphics key terms

A drawing method that shows a three-dimensional object as separate flat views, each looking straight at one face, with the viewing lines parallel to each other and at right angles to the picture plane.

The principal orthographic view obtained by looking at an object from the front; it usually shows the most characteristic shape and is drawn first, with other views aligned to it.

The orthographic view seen from directly above an object, drawn below or above the front elevation depending on the projection convention, and showing width and depth.

A side view of an object taken from the left or right, projected alongside the front elevation to reveal depth and height information not visible in the other two views.

A projection convention in which the object sits between the observer and the picture plane, so each view is placed on the far side of the object; the plan appears below the elevation.

A projection convention in which the picture plane sits between the observer and the object, so each view is placed on the near side; the plan appears above the elevation and the symbol shows a truncated cone.

An additional orthographic view projected onto a plane parallel to an inclined face, used to show the true shape and size of a surface that appears foreshortened in the principal views.

A pictorial drawing in which the three axes are set 120 degrees apart, vertical lines stay vertical, and all three dimensions are drawn to the same scale without perspective convergence.

A pictorial sketch built on isometric axes with dimensions measured full length along the axes rather than reduced, making it slightly larger than a true isometric projection of the same object.

A family of parallel projections in which an object is tilted to reveal three faces at once; isometric, dimetric and trimetric views are members of this group.

A pictorial method in which the front face is drawn true shape and parallel to the picture plane, while receding edges are drawn at an angle, often half scale, to suggest depth.

An oblique projection in which receding lines are drawn at full scale, usually at 45 degrees, producing a deep but distorted appearance compared with cabinet projection.

An oblique projection in which receding edges are drawn at half their true length, reducing the exaggerated depth that appears when full-scale receding lines are used.

The point on the horizon line where parallel receding edges appear to converge in a perspective drawing; one-point and two-point perspectives use one or two such points.

A horizontal line across a perspective drawing representing the observer's eye level; all vanishing points for horizontal receding edges lie on it.

A pictorial method in which objects appear smaller as they recede and parallel edges converge, reproducing the way the eye actually sees depth and distance.

The actual size and outline of a surface as it would appear when viewed perpendicular to it, obtained through auxiliary views or development rather than from a foreshortened principal view.

A flat pattern produced by unfolding the surfaces of a three-dimensional object so they lie in one plane, used to mark out sheet metal or card before folding.

A drawing that shows an object as if cut by a plane, with the cut surface hatched and the interior features behind the cut plane drawn in visible outline.

An imaginary plane passing through an object to expose its interior; its position and direction are indicated by a chain line with arrows on the related view.

Evenly spaced thin parallel lines drawn at about 45 degrees across a cut surface in a section view to distinguish solid material from empty space.

A straight line or curve that touches another curve at exactly one point without crossing it; in geometry, the point of contact is where the two share a common direction.

The geometric procedure for drawing an arc or line that touches a given circle or line at a single point, often used to blend curves smoothly in engineering drawings.

Joining two lines or curves with a smooth arc so the transition has no corner; the arc is tangent to both elements at the points where it meets them.

To divide a line, angle or arc into two equal parts, usually by construction with compass and straightedge rather than by measurement.

A line that cuts a given segment at right angles through its midpoint; every point on it is equidistant from the two ends of the segment.

The set of all points that satisfy a stated geometric condition, such as all points a fixed distance from a given point, which form a circle.

A line or ray that divides an angle into two equal angles; every point on it is the same perpendicular distance from both arms of the angle.

The proportion approximately 1:1.618 in which a line is divided so that the whole is to the longer part as the longer part is to the shorter, often used for balanced rectangles.

The relationship between the sizes of parts of a design or drawing and of those parts to the whole, used to create balance and visual harmony.

The ratio between a drawn length and the real length it represents, such as 1:50 on a site plan or 2:1 on an enlarged detail.

A network of evenly spaced horizontal and vertical guide lines used to position text, images and margins consistently and to keep a layout orderly.

The arrangement of text, images and white space on a page or screen, planned so that information is easy to find and the composition looks balanced.

The selection and arrangement of type, including typeface, size, spacing and hierarchy, to make written content legible and visually appropriate to its purpose.

A complete family of letters, numerals and symbols sharing one consistent design, such as a serif or sans-serif face, available in various weights and styles.

The visual ordering of elements by size, weight, colour or position so a viewer reads the most important information first and supporting detail afterwards.

The deliberate difference between elements in tone, colour, size or weight that makes shapes and text stand out and helps guide the eye through a design.

The empty area left between and around elements in a composition; it separates content, reduces clutter and gives the eye somewhere to rest.

The positioning of elements so their edges or centres line up along a common axis, creating a tidy, ordered appearance and clear visual connections.

A simplified symbol or icon that represents an object, activity or instruction without words, used on signs and in information graphics for quick recognition.

A mark or shape that stands for something else by convention, such as a standard sign for a facility, hazard or direction, understood without explanatory text.

A coordinated system of signs using consistent symbols, type and colour to guide people through a building or public space and identify facilities.

The practice of adding measured values, dimension lines, extension lines and arrowheads to a drawing so a part can be made to the intended size.

The permissible variation in a dimension, stated as upper and lower limits, within which a manufactured part is still acceptable for its purpose.

The system of specifying the maximum and minimum sizes of mating parts and the resulting clearance or interference between them, such as a sliding or press fit.

A standard meaning assigned to each line type, such as continuous thick for visible outlines, dashed for hidden edges and chain for centre lines.

Features of an object that are not visible from the viewing direction, drawn as evenly spaced short dashes to show internal or obscured edges.

A chain line of alternating long and short dashes drawn through the axis of symmetry of a circular or symmetrical feature to locate its centre.

The property of a shape that can be divided into matching halves by a line, or repeated by rotation about a point, so one part mirrors another.

A transformation that changes the size of a shape by a scale factor from a fixed centre point, keeping all angles and the overall proportions unchanged.

The outer boundary or face of a solid object; in graphics it may be flat or curved and is often developed into a flat pattern for manufacture.

A three-dimensional geometric body such as a prism, pyramid, cylinder, cone or sphere, bounded by flat or curved surfaces and having volume.

A continuous part of a circle or other curve, defined by its radius and the two points where it begins and ends.