A thing that is of smaller size, value, importance etc.

“The greater sand hills increasingly do not migrate, but almost all lessers do.”

Of two (or, rarely, more than two) things: the smaller in size (littler), in value, in importance etc.

Small in size.

“This is a little table.”

Insignificant, trivial.

“It's of little importance.”

Very young.

“Did he tell you any embarrassing stories about when she was little?”