Here are some examples of how it's used in English:
* Tenuous: meaning weak, flimsy, or uncertain.
* Attenuate: meaning to make thinner or weaker.
* Tenacity: meaning the quality of being persistent or determined, which ironically comes from "tenuis" as the root word implies a thin thread, but a thread that is strong enough to hold on.
So, while "tenuis" itself is rarely used directly in English, it forms the basis of many words that describe things that are small, weak, or fragile.