ETYM Latin, from Greek, to place, set. Related to Do, Anathema, Apothecary, Epithet, Hypothesis, Parenthesis, Theme, Tick a cover.
In musical analysis, a term borrowed from Greek poetry, denoting a stressed beat (downbeat), usually in comparison with or reference to an arsis, or unstressed beat (upbeat). In German usage, “arsis” and “thesis” have opposite meanings to the original Greek and English words.
(Irregular plural: theses).
An unproved statement put forward as a premise in an argument.