grammar - Is the conditional a mood or a tense?

Is the conditional a mood or a tense? I've heard it described in both ways.

It seems more like a mood as it is often lumped with hypothetical constructions and the subjunctive mood. I could see it too as being a kind of nuance of the future though, as the conditional often implies something that will happen when other conditions are met. For example, "If I were a bird, I would fly away."

People have made a tag that says conditional-mood, but it has only been used three times, so I'm not convinced.

Answer

Traditionally, it is considered neither, though it is sometimes called a mood for lack of a better word. The word function would seem the best term. I am assuming that you are talking about the word would in your example. The adjective "conditional" just means "related to a condition"; when used as a noun, it usually refers to a function of the past subjunctive tense of modal verbs (would, could, might, and should).

There are three traditional moods in English, indicative, subjunctive, and imperative; there are several tenses, which are combinations of moods, aspects, and temporal properties (you might say past and present are aspects, though they are usually not so called).

There are three types of conditional sentences, as Henry has pointed out, which are mainly just sentences in which an explicit or implicit condition is present. There is a function of the past subjunctive that is called conditional because it is used with one of these types, the so-called hypothetical condition (if he were rich, he would be unhappy). I think that is the one you mean; while it is sometimes called a mood, I find this unclear and confusing: how can something be of two moods, both subjunctive and conditional? Function is the term that both fits best with established terminology and best describes what kind of phenomenon it is.