A convenient list of common terms.

Let's put every entry under header section, so it can be easily linked from other pages.


  • Actor
    An object that can be placed into a level, supporting translation, rotation and scale. All objects in a level inherit from the Actor class.

  • Apex
    Physics engine by Nvidia, more on the Apex Framework. The plugin is no longer supported and thus disabled by default. It is going to be replaced by Chaos destruction systems.

  • Asset
    An element used when creating a game. Imported or created within the editor. Textures, 3D objects, sounds, blueprints, etc.


  • Blueprint (BP)
    Visual Scripting language used in UE4.

  • Breakpoint
    A debugging tool that lets you pause code execution (either C++ or Blueprints) at a specific point.


  • Call Stack
    A list of function calls in the order they were executed.

  • Class Default Object (CDO)
    The template object created for UCLASSs. Can be accessed using


    or by Get Class Default Object node in blueprints. Pro-tip: you can get a variable's default value (what was set before running a game) by accessing CDO and then simply getting variable value. This way you need only a single variable "health" instead of "max health" and "current health".

  • Chaos
    Physics and destruction system by Epic Games.

  • Cascade
    Particle effects system used in Unreal Engine 3 and 4, planned to be superseded by Niagara.


  • Gameplay Ability System (GAS)
    UE4 Plugin / framework used for implementing gameplay abilities.

  • Gameplay Framework
    The set of foundation classes in UE4 used to build a game. This includes core classes such as GameMode, GameState, PlayerState etc.

  • Garbage Collection
    The process by which no longer needed UObjects are cleaned up during runtime. Both UObjects flagged for destruction as well as the ones not being referenced anymore are removed automatically by UE4.


  • Hot Reloading
    Keeping a program running while changes are made to its files and then having it reflect those changes. For example, every time you edit your C++ or Blueprint code and compile, hot reloading lets you see the changes in UE4 Editor without having to restart it.


  • Logging
    Recording internal game events or data in a text file.


  • Matinee
    Cinematic production tool in Unreal Engine 3 and 4. It hasn't been updated at all after the official release of UE4. Entirely replaced by Sequencer and deprecated in UE 4.23.


  • Niagara
    New Particle effects system in Unreal Engine 4.


  • Profiler
    UE4 tool for collecting information on the performance of your game.

  • Property Replication
    Properties on Actors can be set to replicated. This causes the server to send an update to clients every time the property changes.


  • Remote Procedure Calls (RPC)
    RPCs are functions called over the network. Useful when implementing multiplayer to allow the server to execute functions on clients and vice versa.

  • Replication
    The process of synchronizing data between server and clients. This is used in multiplayer games to keep the game state in sync.

  • Repository (Repo)
    The server where your project is stored, usually using a Source Code Control system such as git, Perforce, or Subversion. When submitting our work to server, we often say pushing to repo or committing to repo. And downloading the recent version of project from there is called updating the repo.


  • Slate
    C++ UI framework

  • Sequencer
    Cinematic production tool for Unreal Engine 4.


  • Unreal Automation Tool (UAT)
    Tool to automate various aspects of UE4 development. For example, the BuildCookRun automation tool Builds, Cooks, and Runs a project.

  • Unreal Build Tool (UBT)
    The build system used by UE4. All other tools, for example Visual Studio projects, end up running UBT to perform the build.

  • Unreal Game Sync (UGS)
    Project synchronization tool for larger teams using Perforce.

  • Unreal Header Tool (UHT)
    A C++ header parser and code-generation tool that is run before the standard C++ compilation. Used to implement parts of the UE4 UObject system.

  • Unreal Motion Graphics (UMG)
    A visual UI authoring tool and collection of widgets. Built on top of Slate.

  • Unreal Shader File (USF)
    HLSL like shader files that implement part of the UE4 rendering system.

  • Unreal Shader Header (USH)
    HLSL like shader files headers that implement part of the UE4 rendering system.

Updated ago