Terms

Duration - The element of time in music
Beat - the underlying pulse in a piece of music. Steady, and not always "heard", but more "felt".
Rhythm - an organized and repeating pattern of beats and syncopations forming a musical idea. (I've modified this to " an organized and repeating pattern of shorts and longs forming a musical idea".)
Tempo - the speed of the beat. Fast, slow, moderate, etc.
Meter - the automatic breaking up of beats into patterns of two or three in our ear when we hear music. "How the beats are grouped".
Nonmetric - when the beat is not evident.

Dynamics - The relative loudness or quietness of musical sound (Volume)
Crescendo - gradual increase in volume
Decrescendo - gradual "decrease" in volume
Subito - a sudden change in the dynamic level. It may move from loud to soft or from soft to loud, but it is abrupt.