This isn’t exactly a word you’ll find easy to slip in to everyday conversation, but it’s nevertheless one of those interesting pieces of trivia that tells you the name for something you’ve heard your entire life.

synecdoche (syn·ec·do·che): / si NEHK duh kee /
noun

(1) a figure of speech in which a whole is used to represent a part or a part is used to represent a whole, or the specific for the general or the general for the specific, as in “five sail” for “five ships” or “the law” for “police officer” or “thief” for “pickpocket”

[Via Middle English ‘syndoches’ from Latin syndoche from Greek sunekdohke meaning “interpretation, sense,” from sunekdekhesthai meaning “to take on a share of,” from ekdekhesthai meaning “to understand, receive.”]

Usage: I found this student’s continual reference to humans as “creatures” to be a rather precise and telling synecdoche.