vulnus

Vulnus, vulneris, n., is third declension. The nominative hides the stem: everything after it runs on vulner-, so vulnere, vulneribus, vulnera. Older texts and most manuscripts write volnus, and since scribes used u for both u and v you will meet it as uulnus on the page.

The word covers a physical wound and, without much of a jump, a blow to reputation, treasury or state - vulnus rei publicae is ordinary prose, not purple. The verb is vulnero, "I wound", and that is the form English borrowed for "vulnerable", which strictly means woundable rather than fragile. Do not confuse the genitive vulneris with vulgus, "the crowd"; they look nothing alike until you are reading fast.