Usage groups are groups of definitions. They differ from [Usage nodes][usage] as they all belong to the same part of speech, but differ based on their meaning. For example, the verbal phrase to "pass out" might have the definitions:
to hand out, especially to a large group of people
yet can also mean:
to lose consciousness
It is important to distinguish between these verb definitions so the definition list does not become muddled. While groups are not required, they are encouraged, especially for lengthy usage nodes.
No, but recommended