vidvino

Vidvino is vidvo plus -in-, the suffix that makes the female counterpart of a root. The base vidvo, a widower, has no page of its own here yet, so hold it in your head as the parent word: it is a man whose wife has died, and adding -in- gives the woman whose husband has died.

That is worth pausing over, because it inverts the history. In Latin the word was feminine to start with - vidua was the widow, and Latin had to build viduus for the man. Esperanto's system runs the other way round: the bare root is the default, and -in- marks the female, so the language ends up deriving the older of the two meanings from the newer. It is one of the places where the affix system is visibly a design rather than an inheritance, and one of the places critics point at when they argue the default should never have been male. The verb is vidviĝi, to be widowed.