precaution

A precaution is something done in advance to avoid trouble. Take precautions, as a precaution, a sensible precaution.

As a precaution is the standard formula for an action taken when nothing has gone wrong yet — taken to hospital as a precaution. Take precautions is also a common euphemism for contraception. The precautionary principle is the policy idea that where harm is possible but unproven, you act as though it were likely. Note precautionary, and that a precaution is judged by what it prevents and is therefore always invisible when it works.