How is the use of the word
theory in science different from its more
common use?

In science a theory is supposed to be valid and we use it as if it were true in all cases.

Explanation:

In science a theory is considered proven (untill somebody would be able to disprove of it). In science a theory is supposed to be valid and we use it as if it were true in all cases.

In common language, a theory is more like a guess.

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