animal

Animal, animalis is a third declension neuter i-stem, so the ablative singular is animali, the nominative and accusative plural animalia, and the genitive plural animalium. It comes straight from anima, "breath, soul": an animal is a thing that breathes.

That origin is why Latin can call a person an animal without insult. Homo est animal rationale is a definition, not abuse, and any translation that renders it "beast" has gone wrong. Where English wants "beast" in the brutish sense, Latin reaches for bestia or fera. The gender catches learners out constantly: it is neuter, so magnum animal, never magnus.