Lookup

Glossary

84terms you'll hear in a project meeting. Each one has the definition and, where it matters, the misunderstanding that costs people time.

Core concepts6

BIMBuilding Information Modeling: The practice of building a single coordinated database of a building — geometry plus data — and deriving drawings, schedules, and analysis from it rather than drawing each output by hand.; BIM is a process, not a file format and not Revit. A 3D model with no data in it is just 3D CAD.; See alsoLOD CDE
Parametric: Geometry driven by named values and relationships rather than fixed coordinates. Change the value, the geometry updates everywhere.; This is the whole reason Revit is slower to start and faster to change than CAD.
Single source of truth: The idea that a given fact — a door width, a room name, a level elevation — is stored in exactly one place in the model and read everywhere else.; When you find yourself typing the same number twice, you've broken it. Use a parameter or a tag instead.
LODLevel of Development / Level of Detail: An agreed measure of how reliable model content is, usually on the AIA scale LOD 100 (massing) through 500 (as-built verified).; Level of Development (reliability of the information) and Level of Detail (visual complexity) are different things that share the acronym. Ask which one someone means.
BEPBIM Execution Plan: The project document that defines who models what, at what LOD, on which coordinate system, with what naming conventions, and how files are exchanged.; If you're joining a project, read the BEP before you open Revit. It answers most of the 'why is it set up like this' questions.; See alsoLOD CDE
Project vs. family file: `.rvt` is a project: the building, its views, and its sheets. `.rfa` is a family: one reusable component definition, edited in the Family Editor. `.rte` is a project template; `.rft` is a family template.; Four extensions, and mixing them up is the most common beginner stumble. Templates create new files; they aren't linked afterwards.

Elements & families13

Category: The top level of Revit's built-in classification: Walls, Doors, Windows, Structural Columns, Mechanical Equipment. Fixed by Autodesk — you cannot invent one.; Category controls visibility, graphics, tag type, and schedule availability. Choosing the wrong category when you create a family is expensive to fix later.; See alsoFamily Type Instance
Family: A definition inside a category — 'Single-Flush' doors, 'Basic Wall'. Holds the geometry rules and which parameters exist.; See alsoType Instance Loadable family
Type: A named variant of a family with specific values — 'Single-Flush: 36" x 84"'. Change a type parameter and every instance of that type changes.; Category → Family → Type → Instance is the hierarchy that explains most of Revit's behavior. Learn it before anything else.
Instance: One actual placed element in the model. Instance parameters (sill height, comments, room number) vary per instance.
System family: Families that only exist inside a project and are built from layer definitions: walls, floors, roofs, ceilings, stairs, railings, ducts, pipes.; You can't save a system family to its own file. Move them between projects with Transfer Project Standards or copy/paste an instance.
Loadable family: A component saved as its own `.rfa` and loaded into projects: doors, windows, furniture, plumbing fixtures, most equipment.
In-place family: A one-off model element created directly in the project rather than in a separate file.; Convenient trap. They bloat the file, can't be scheduled cleanly across projects, and are hard to reuse. Use them for genuinely unique geometry only.
Host / hosted element: A door or window is hosted by a wall; a light fixture may be hosted by a ceiling. Delete the host and the hosted element goes with it.; Hosting across a linked model is possible but fragile — it breaks when the link is reloaded or the host moves. Most standards ban it.
Reference plane / reference line: Invisible planes inside a family used to drive and constrain geometry. Give them names so you can pick them in dimension constraints.; In the Family Editor, dimension between reference planes and flex those first. Geometry follows planes; planes should not follow geometry.
Constraint: A locked dimension, alignment, or 'attach top/base' relationship that forces elements to keep a geometric relationship.; Over-constraining is the #1 source of 'Revit won't let me move this' errors. `RC` reveals constraints in a view.
Toposolid: The modern site/terrain element (Revit 2024+). A true solid with thickness and material layers, replacing the older Toposurface.; Unlike the legacy Toposurface, a Toposolid can host floors and be sculpted with sub-elements, and it schedules like a real element.
Curtain wall: A wall type made of a grid, mullions, and panels rather than material layers. Panels can be glass, solid, or other wall types.
Group vs. assembly: A Group is a repeated set of elements edited in one place (hotel rooms, typical apartments). An Assembly is a set of elements documented together with its own auto-generated views and sheet.; Groups are for repetition; assemblies are for fabrication documentation. Groups with hosted/attached elements are notoriously fragile.

Views & graphics13

View: A live query into the model: plan, section, elevation, 3D, drafting, legend, schedule. Views are not drawings you edit — they're filtered windows onto one model.
View range: The set of horizontal planes controlling what a plan view shows: Top, Cut Plane, Bottom, and View Depth.; 'My element isn't showing up' is a view range problem about half the time. Check the cut plane before you check anything else.; See alsoPlan region Visibility/Graphics overrides
Plan region: A sub-area of a plan view with its own view range — for a clerestory window or a split-level floor.
Visibility/Graphics overridesVV or VG: Per-view control of which categories are visible and how they draw. Opened with `VV`/`VG`.; Revit's graphics precedence, weakest to strongest: object styles → view template → V/G → filters → element override. Element overrides are why one wall is inexplicably red.
View template: A saved bundle of view settings — scale, detail level, V/G, filters, phase — applied to many views at once.; The single biggest lever on documentation consistency. Set every view's graphics through a template, not by hand.
View filter: A rule-based selection ('all walls where Fire Rating = 2 HR') with graphic overrides attached, applied per view or via a template.
Detail level: Coarse / Medium / Fine. Families can show different geometry at each level, so a 1:100 plan stays readable.
Scope box: A 3D box that crops a set of views and controls which grids and levels appear in them.; The right way to manage matchlines and per-area plans on big projects. Assign views to scope boxes instead of cropping each one.
Crop region: The rectangle bounding what a view shows. Has a separate 'annotation crop' that clips tags and dimensions.
Reveal Hidden Elements: The lightbulb toggle (`RH`) that shows everything hidden in a view in magenta so you can un-hide it.; Use it before you conclude an element was deleted.
Phase / phase filter: Every element has a 'Phase Created' and 'Phase Demolished'. A view's phase and phase filter decide whether it draws as new, existing, demolished, or temporary.; Renovation work lives or dies on phases. Getting the phase wrong makes elements vanish from a view with no error.
Design option: A mechanism for modeling competing versions of part of the building in one file, with each view showing a chosen option.; Powerful, but elements inside options behave differently — they can't be edited from the main model. Accept the primary option as soon as the decision is made.
Worksharing display: A view mode that colors elements by owner, workset, model updates, or checkout status.; The fastest way to answer 'who has this element checked out?'

Documentation12

Sheet: A virtual piece of paper with a title block on which you place views. Sheets are what gets printed and issued.
Title block: The family defining a sheet's border and its label fields — project name, sheet number, revision block.
Viewport: The instance of a view placed on a sheet, with its own type controlling how the view title line and label draw.; A view can only be placed on one sheet. If you need it twice, duplicate the view (or use a Legend, which can repeat).
Annotation vs. model element: Annotation (tags, dimensions, text, symbols) lives in one view and scales with the view. Model elements exist in 3D and appear in every view that sees them.; Annotation families are drawn at paper scale; model families at real size. Choosing the wrong family template is a redo.
Tag: An annotation that reads a parameter value off the element it points at, so the drawing updates when the model does.; If you're typing a value into a text note that already exists as a parameter, use a tag instead.
Keynote: A tag driven by an external keynote text file, giving consistent numbered notes across the whole set.
Schedule: A live tabular view of the model — door schedules, room areas, wall quantities. Editing a schedule cell edits the model.; Schedules are the best model-auditing tool in Revit. Schedule for QC even when you'll never print it.
Legend: A view showing symbolic representations of families and annotation for reference. The only view type that can be placed on multiple sheets.
Drafting view: A 2D-only view with no connection to the model — used for standard details imported or drawn by hand.
Revision / revision cloud: Managed issue tracking: clouds and tags are tied to a revision defined in Sheet Issues/Revisions, and appear automatically in the title block revision schedule.; Never draw a revision cloud with detail lines. Use the real tool or your revision block will lie.
Matchline: The annotation showing where a plan splits across sheets, paired with a view reference. Driven by scope boxes.
Witness line: The individual reference of a dimension string. You can add, remove, and move witness lines without redrawing the dimension.

Data & parameters12

Parameter: A named piece of data on an element, type, or project. Can be a length, number, text, yes/no, material, or another element.
Type vs. instance parameter: A type parameter is shared by every element of that type; an instance parameter is unique per element.; Ask 'would every one of these change together?' If yes, type. If no, instance.
Project parameter: A parameter added to categories inside one project. Schedulable, but not taggable and not portable to other files.
Shared parameter: A parameter defined in an external `.txt` file with a stable GUID, so the same parameter means the same thing across families, projects, and schedules.; The only kind you can tag AND schedule AND round-trip through families. If you want a parameter to survive real project life, make it shared. Guard that shared parameter file — regenerating it creates new GUIDs and silently orphans your data.; See alsoGUID Global parameter
Global parameter: A project-wide value that can drive dimensions and other parameters — one place to set 'typical corridor width'.
Formula: An expression driving one parameter from others. Case-sensitive parameter names, and conditionals look like `if(Width > 900, 2, 1)`.; Units bite here: dividing two lengths gives a number, and Revit will refuse the formula if the resulting unit doesn't match the parameter type.
GUID: The globally unique id behind shared parameters (and elements, via `UniqueId`). Matching is by GUID, not by name.
Element ID: The per-document integer identifying an element. `Manage → Select by ID` jumps straight to it; warnings and error logs report them.; Element IDs are not stable across files or copy/paste. `UniqueId` is the one that persists.
Room: A bounded volume carrying name, number, area, volume, finishes, and occupancy. Bounded by room-bounding elements and room separation lines.; A room with nothing bounding it becomes 'Not Enclosed' and its area reads zero. Rooms deleted from a plan may still exist as unplaced rooms — purge them.
Area / area scheme: A separate boundary system from rooms, used for gross/rentable area calculations under a named scheme (BOMA, gross building).
Key schedule: A schedule of named presets. Assign a key to an element and every parameter in the key fills in automatically.; The cleanest way to manage room finishes: define 'Office' once, apply it to 200 rooms.
Calculated value: A schedule-only column computed from other fields, without adding a parameter to the model.

Collaboration13

Worksharing: Revit's multi-user mode. A central model holds the truth; each person works in a local copy and exchanges changes by synchronizing.; See alsoCentral model Workset Synchronize with Central
Central model: The master file (on a server or in Autodesk Construction Cloud) that everyone syncs to.; Never open the central file directly to work in it. Always work in your local copy.
Local file: Your personal copy of the central model, created by opening the central with 'Create New Local'.; Make a fresh local at the start of each day. Stale locals cause the strangest sync errors.
Workset: A named group of elements used for ownership and bulk visibility control — 'Shell', 'Interiors', 'Level 2 MEP'.; Worksets are about who owns what and what you can unload for performance. They are not a substitute for categories or filters.
Synchronize with CentralSTC: Push your changes to central and pull everyone else's. Relinquish your borrowed elements as part of it.; Sync often, relinquish always, and never sync while someone else is mid-sync on a file-based central.
Element borrowing: Editing an element automatically requests exclusive ownership of it until you relinquish.; 'Can't edit the element until it's released' means someone else is borrowing it — the Worksharing Display and the request dialog will tell you who.
Link: A reference to another Revit, IFC, CAD, or point-cloud file. Its content shows up but is owned and edited elsewhere.; Link, don't import. Imported CAD drags in line styles, layers, and bloat that are painful to purge.
Copy/Monitor: A tool that copies levels, grids, columns, or MEP fixtures from a linked model and warns you when the original moves.; This is how structural and architectural teams keep grids honest across disciplines.
Interference check / clash detection: Finding physical overlaps between elements. Revit has a basic built-in check; Navisworks does it properly across all trades.
CDECommon Data Environment: The agreed single place where project information is shared — for Autodesk projects, usually Autodesk Construction Cloud / BIM Collaborate Pro.
Shared coordinates: The mechanism that lets multiple files agree on real-world position and rotation via Acquire/Publish Coordinates.; Project Base Point, Survey Point, and Internal Origin are three different things. Getting them wrong is the classic cross-discipline coordination failure.; See alsoProject Base Point vs. Survey Point
Project Base Point vs. Survey Point: The Project Base Point is the project's local 0,0 reference. The Survey Point is the real-world surveyed reference. The Internal Origin is Revit's invisible true origin, and models should stay within about 20 miles of it.; Never move the Internal Origin — you can't. Keep the model near it or accuracy and view behavior degrade.
Audit / Purge Unused / Compact: File hygiene: Audit checks and repairs internal integrity on open, Purge Unused removes unused families and types, Compact rewrites the file smaller on sync.; Audit weekly on a big central model, not every open — it's slow and it rewrites the file.

Interop & standards6

IFCIndustry Foundation Classes: The open, vendor-neutral building data format (buildingSMART). The usual way to hand a model to someone who doesn't use Revit.; IFC export quality depends entirely on your category and property-set mapping. Test the export early, not the week of the deadline.
COBie: A spreadsheet-shaped standard for handing over asset data (equipment, spaces, warranties) to the facility operator.
NWC / Navisworks: The lightweight export consumed by Navisworks for federated coordination, clash detection, and 4D sequencing.
ISO 19650: The international standard for managing information over a built asset's life cycle — naming, states, approval, and the CDE workflow.
ACCAutodesk Construction Cloud: Autodesk's cloud platform. BIM Collaborate Pro is the entitlement that enables cloud worksharing for Revit models hosted there.
DWG export layer mapping: The table controlling which AutoCAD layer each Revit category exports to, usually configured once from a company standard file.

Automation9

Dynamo: The visual programming environment shipped with Revit. Wire nodes together to read and modify the model in bulk.; Best for one-off data operations and geometry generation. Ships in the box, so it's the lowest-friction place to start.
pyRevit: A free, open-source add-in that gives you a scripting environment, a large library of ready-made tools, and a fast way to publish your own Python buttons to the ribbon.; The pragmatic middle ground: real code, no C# project, no compile step, and a hot-reload workflow.
Revit API: The .NET API exposed by `RevitAPI.dll` and `RevitAPIUI.dll`. Add-ins implement `IExternalCommand` or `IExternalApplication` and are registered with a `.addin` manifest.; See alsoTransaction ExternalEvent / modeless UI
Transaction: Any change to a Revit document must happen inside an open `Transaction`, which you then `Commit()` or `RollBack()`. This is what makes undo work.; 'Attempting to modify the model outside of transaction' is the first error every Revit developer hits.
FilteredElementCollector: The API's query object. Chain category, class, and parameter filters to pull elements out of a document efficiently.; Always apply a quick filter (category/class) before a slow filter (parameter value), or you'll expand every element in the model.
ExternalEvent / modeless UI: The mechanism for touching the model from a non-modal window or background thread — you raise an event and Revit runs your handler in a valid API context.; The Revit API is single-threaded. All model access happens on Revit's main thread, full stop.
Idling event: An application-level event fired when Revit is idle, historically used to run deferred work safely.
IronPython vs. CPython: IronPython (2.7/3.4) runs on .NET and can touch the Revit API directly. CPython is standard Python and reaches .NET through a bridge, but gets the real package ecosystem.; pyRevit and Dynamo both let you choose. Pick CPython when you need numpy/pandas-class libraries, IronPython when you want frictionless API access.
Model data extraction: Getting model data out for analysis — schedule export to CSV, ODBC export, the Revit API, or the cloud-side AEC Data Model / Autodesk Platform Services APIs.; If someone just needs numbers, a scheduled CSV export beats a custom add-in nine times out of ten.