Radioactive contamination: things don't transfer the property of radioactivity to everything they touch and/or irradiate. If that were the case, the entire ~~Earth~~ universe would have become radioactive gray goo long, long ago.

When radiation workers talk about "contamination," we mean radioactive compounds have physically transferred from one object onto/into another. For example, tools becoming contaminated with radioactive metal dust from equipment they touch, or clothing absorbing radioactive iodine gas from the air.

There is a form of radiation called neutron radiation that does make some formerly stable things (mainly metals) radioactive. This isn't something you're likely to encounter unless you're a specific type of radiation worker, however.

This is mainly gear-grindy to me because the reason we don't have gamma-sterilized produce in the US is completely unfounded fear that gamma irradiation "contaminates" everything it touches. So we could be having lovely fresh strawberries and peppers that last weeks longer than they usually do, but no, we can't because rAdIaTiOn ScArY 🙄