What primarily differentiates the term 'gravel' from a 'pebble'?

Answer

Gravel is a collective category encompassing pebbles and smaller materials.

A pebble is a specific size class, whereas gravel describes a mixture or general state of being composed of many particles, often encompassing pebbles and materials larger than sand size.

What primarily differentiates the term 'gravel' from a 'pebble'?
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