Timing

Timing is an important consideration in animation. They are two forms of timing to consider in making an animation - physical timing and theatrical timing.

Physical timing is the timing of motions for the purposes of making a scene realistic. For example, when a character is trying to move an object, the object's weight determines how long it takes to move from a still start. If its an heavy object, it'll take a long bit of time to start moving, while if it was a light object, it'll take almost no time at all.

Here's a simple animation of a man pushing a large box demostrating the use of physical timing.

Another example is the timing of sound sources, such as a character's mouth, parallel to a soundtrack.

Theatrical timing is the timing of things for dramatic purposes. For example, the character's entry to a scene can be slow to produce tenson or mystery or fast to suprise the viewer or to make a character appear normal or average or not interesting.