quo

Quo is a Latin word with multiple related uses. In classical Latin, quo is the ablative singular form of the relative pronoun qui and also an adverb meaning “to which place” or “where to.” As an ablative of direction, it marks movement toward a destination and is often translated as “to which” or “to where.”

In Latin phrases, quo appears in questions and expressions of movement. A well-known example is Quo vadis? meaning “Where are you going?” The phrase uses quo to express the idea of going toward a place.

Quo also appears in several enduring English loan phrases. In quid pro quo, the expression means “something for something” or “this for that,” describing a reciprocal exchange. In quo warranto, a historical legal term, the phrase translates roughly as “by what warrant” or “by what authority,” and it was used to challenge a person’s right to hold office or exercise power.

Grammatically, quo is the masculine and neuter ablative singular of qui; the feminine form is qua. It contrasts with quod (neuter nominative and accusative) and with qua (feminine ablative). In modern use, quo survives primarily in fixed phrases and quotations, especially within legal, literary, and historical contexts.