intro

Intro, intrare, intravi, intratum, first conjugation, formed from the adverb intra, "within". Both constructions are good: intrare in urbem with the preposition, and intrare urbem with a plain accusative, the second commoner in verse and in later prose.

Two things to keep straight. Intro is also an adverb meaning "inwards, to the inside", as in intro ire, "to go in" - and since the verb was built on that family the resemblance is real, not coincidence. Second, classical prose prefers ineo, ingredior or introeo where the ecclesiastical and medieval corpus simply writes intro, so a text thick with intravit is telling you its date. French entrer, Spanish entrar and Italian entrare all descend from it, and English enter and entrance come by that road; introduce is intro- plus duco, a different formation from the same nest.