One who behaves in a certain way; a person characterized by particular behavioral patterns or actions.
From behave + -er (agent suffix). The -er suffix creates agent nouns (one who does the action), though 'behaver' is rarely used compared to 'behavior' or 'behaviorist.'
Behaver is logically constructed but sounds odd—we prefer 'person' or just describe the behavior itself rather than calling someone a 'behaver,' showing how some grammatically valid words just don't feel natural to English ears.
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