AutoCAD Vocabulary Reference
The words matter. Know what you're talking about before you start drawing so you can communicate with your colleagues.
Why this matters
When something breaks in class — and it will — you need to be able to describe the problem accurately to get it fixed efficiently. "My lines look weird" is not a diagnosis. "My linetype scale is wrong in the viewport" is something that can be solved in 30 seconds. Learn the vocabulary before you need it.
Core concepts
| Term | What it is |
|---|---|
| Model Space | Where all drawing geometry lives, at 1:1 real-world scale. A 200-foot road is drawn as a 200-foot road. |
| Paper Space | Where you set up the printed sheet — dimensions represent inches on the output page, not feet in the world. |
| Layout Tab | Each Layout tab is a separate Paper Space environment. You can have multiple layouts (multiple sheets) in a single drawing file. |
| Viewport | A window cut through Paper Space that displays Model Space content at a defined scale. Think of it as a camera pointing at your model from above. |
| Layer | A named graphic channel. Every object in a drawing lives on a layer. Layers control color, linetype, lineweight, visibility, and printability for all objects assigned to them. |
| XREF (External Reference) | A linked drawing file that appears in your drawing but lives in a separate file. Changes to the source file update in your drawing automatically. The survey drawing is an XREF. |
| Block | A reusable symbol definition stored in the drawing. One definition, many placed instances. Edit the definition and all instances update. |
| Hatch | A fill pattern applied within a closed boundary. Represents materials and surfaces on plan drawings. Never explode a hatch! |
| Linetype | The dash/dot pattern of a line — Continuous, Dashed, Center, Phantom, Divide, Fenceline, etc. Communicates element type and condition. |
| Lineweight | The physical width of a plotted line, in millimeters. Controlled by the color-to-lineweight mapping in the CTB pen settings file. |
| CTB (Color-Dependent Plot Style Table) | A file that maps AutoCAD colors to output lineweights. The Dave_Purdue.ctb file defines the lineweight standard for this course. |
| Annotative Scale | A system that automatically adjusts the size of text, dimensions, and linetypes based on the viewport scale. Create once, display correctly at any scale. Define this BEFORE drawing content. |
| eTransmit | AutoCAD's file packaging command. Bundles a drawing with all its referenced files (XREFs, images, fonts, pen settings) into a single archive for delivery or archiving. |
| Purge (PU) | Removes unused named objects from the drawing file — layers with no objects, block definitions with no instances, unused linetypes and text styles. Keeps files clean and lightweight. |
| Audit (AU) | Checks the drawing file for structural errors and offers to repair them. Run before any major submission. |
| UCS (User Coordinate System) | Defines the orientation of the X,Y coordinate system. Aligning the UCS to an angled object (UCS OB) makes it easy to draw perpendicular to that object — critical for section construction. |
| OSNAP (F3) | Object Snap. Constrains the cursor to geometrically exact points on existing objects: endpoints, midpoints, intersections, centers, perpendicular points, etc. |
| Polyline (PL) | A connected sequence of line and arc segments treated as a single object. The standard drawing element for all site geometry in this course. Never use simple lines. |
| Dynamic Input (F12) | On-screen coordinate and command input that follows the cursor. An alternative to reading the command line — useful for coordinate entry without looking away from the drawing. |
| PEDIT (PE) | The polyline editor. Closes open polylines, joins separate segments into one, adjusts width, and edits individual vertices. |
From the office
The most common source of confusion in shared CAD files is terminology. "Block" and "XREF" are not interchangeable — they describe fundamentally different things. "Layer" and "color" are not the same — color in this system is a proxy for lineweight, not a visual style choice. Using these terms correctly is what separates someone who understands the system from someone who is guessing their way through it.