An organism that lives in groups or herds, or a person who prefers living in communities.
From Latin gregarius (of the flock) plus -an (denoting a person or being). Constructed similarly to words like 'vegetarian' and 'librarian'.
The naming pattern here reveals how English creates new terms by adding '-an'—the same root gives us vegetarian, humanitarian, and librarian, all 'people who do or prefer something specific.'
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