The vocabulary of motion design — from the 12 principles to the graph editor. Twenty-two terms every practitioner should know.
ARC
Natural motion follows curved trajectories, not straight lines. Objects that move in pure linear paths feel mechanical and lifeless. The arc is nature's default movement path.
ANTICIPATION
A preparatory motion in the opposite direction before the main action. Increases impact and readability. The wind-up before the throw — one of Disney's 12 principles.
BEZIER CURVE
A parametric curve defined by anchor points and control handles. The mathematical foundation of motion paths, easing curves, and vector shapes in every major motion tool.
BLEND MODE
How a layer combines with layers below it. Screen (brightens), Multiply (darkens), Overlay (contrast), Add (luminosity). Compositing's fundamental grammar of light interaction.
COMPOSITING
The process of layering multiple visual elements to create a unified image. From background plates to particle effects — compositing is the assembly phase of motion design.
EASING (SLOW IN/OUT)
The acceleration and deceleration of motion over time. Ease in = accelerates from rest. Ease out = decelerates to rest. Ease in-out = both. Linear motion always looks mechanical.
EXPRESSIONS
JavaScript-based code in After Effects that procedurally controls property values. wiggle(), loopOut(), thisComp.layer() — expressions unlock fully generative animation behavior.
FOLLOW-THROUGH
Parts of an object continue moving after the main body has stopped. A character's hair keeps swinging after they halt. Communicates weight, physics, and organic system behavior.
FRAME RATE
Frames per second (fps). 24fps = cinematic. 30fps = broadcast. 60fps = gaming/UI. Higher rates feel smoother but less "filmic." Motion blur compensates at lower frame rates.
INTERPOLATION
The calculation of in-between values between keyframes. Linear interpolation = constant rate. Bezier interpolation = custom velocity curve. Hold interpolation = no change between keys.
KEYFRAME
A marker at a specific time that defines a property's value. The software interpolates between keyframes to generate motion. The fundamental unit of timeline-based animation.
KINETIC TYPOGRAPHY
Text that moves — letterforms animated to amplify meaning, emotion, or rhythm. The motion becomes inseparable from the message. From Saul Bass to contemporary title design.
LAYER
A single element in a composition — footage, shape, text, solid, camera, light, or null. Layers stack in the timeline and composite in the viewport. The atom of compositing.
MOTION BLUR
The blurring of fast-moving objects across frames, simulating camera shutter exposure time. Essential for natural-feeling motion — without it, fast movement appears strobed and harsh.
NULL OBJECT
An invisible layer used as a parent control. Animate the null, and all children follow. Used for camera rigs, grouped layer control, and expression targets in complex compositions.
OVERSHOOT
Motion that goes past its target before settling back. Communicates energy and elasticity. The classic "bounce settle" that makes UI motion feel alive rather than mechanical.
PRECOMP
Pre-composition: collapsing multiple layers into a single composition layer. Organizes complexity, enables effects on groups, and is essential architecture for any complex motion piece.
SECONDARY MOTION
Additional motion generated by the primary action — a tail following its body, fabric rippling after a gesture. Adds depth and believability to every element in the frame.
SPACING
The distance between consecutive animation frames. Close spacing = slow motion. Wide spacing = fast motion. Spacing IS the velocity — adjusting it is how animators control perceived speed.
SQUASH AND STRETCH
Deforming an object at the extremes of its motion to communicate weight and elasticity. The most powerful of Disney's 12 principles — it makes everything feel physically real.
STAGING
Presenting an idea clearly so it is unmistakable. In motion, staging means silhouette, timing, and composition all work together to direct attention to exactly one thing at a time.
TIMING
How long an action takes to complete. Slow timing = weight, drama, importance. Fast timing = lightness, comedy, energy. Timing is the single most expressive variable in animation.