Here are some other related terms:

* Unreactive: This term implies that the substance does not readily participate in chemical reactions.

* Stable: This term refers to a substance that resists change and does not readily undergo chemical reactions.

* Non-reactive: This term is synonymous with unreactive and inert.

It's important to note that the terms inert, unreactive, and stable can be relative. A substance that is inert under certain conditions may become reactive under different conditions, such as high temperatures or in the presence of a catalyst.