A woman who makes strong or confident claims or assertions about something.
From assertor + -ess (feminine suffix). This forms a gender-specific version of assertor, following the pattern of other -ess nouns (actor/actress, waiter/waitress). The base comes from Latin asserere.
The -ess suffix was once the standard way to mark female versions of nouns, but it's largely fallen out of use in modern English as we move toward gender-neutral terms. Assertress is a relic of this older system!
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