もっとも

もっとも starts a second sentence that takes some of the force out of the first: "mind you", "though", "having said that". The first statement still stands, and もっとも adds the catch. It comes at the head of the new sentence, followed by a comma, and that sentence often trails off in が or けど.

もっとも belongs to writing and careful speech. In conversation the same afterthought usually comes with まあ or a plain けど.

もっとも or ただし

ただし attaches a condition or an exception, the way a rule or a notice does, and its sentence is a flat statement. もっとも is the speaker's own afterthought.

Usage notes

These are other words read もっとも.

もっともだ, "reasonable"

As a な-adjective, もっともだ means "quite right", "understandable".

最も, "most"

もっとも最も is the superlative, "the most". It is usually written in kanji, which keeps it apart.