assume

To assume something is to accept it as true without being fully certain. It's like building a little castle in the air—you can start from a useful idea, but that idea may still float above solid ground. You might assume your friend likes chocolate because they always choose chocolate desserts, even though you haven't asked them directly. Or a detective might assume a suspect had a motive from limited clues, which can be practical for a hunch but risky for a conclusion. It can also mean to take on a role or responsibility, as when a king assumes the throne.

The word "assume" has a useful split personality. Most often, it means to accept a proposition as true without enough evidence yet. In ordinary conversation, this might be a helpful shortcut, as in, "I assumed she was coming because she seemed interested." In analysis or science, people may say "assuming X is true, then Y follows," treating the claim as a starting point rather than proven fact. In both cases, it is a guess that should be tested before it hardens into truth.

More formally, assume means to take on a role, responsibility, or authority: a prince assumes the throne, a company assumes the debts of a failed partner, or a pilot assumes command of a flight. Closely related is the idea of adopting a style, posture, or expression—someone may assume an air of indifference to keep nervousness hidden. In these uses, the word suggests an intentional taking-on of something and can involve personal, social, or legal responsibility.

Its root is Latin assumere, "to take to oneself." That origin fits all its meanings: whether we assume an idea, a position, or a persona, we are actively taking something on first and checking later.