Tragoedia in proscaenio incipit.

Because in is showing location, not motion.

With in, Latin usually works like this:

• in + ablative = in/on/at a place, meaning where?
• in + accusative = into/onto a place, meaning to where?

So:

• in proscaenio = on the stage / in the stage area
• in proscaenium would mean something like into the stage area

Here the tragedy is beginning there, not moving into it, so the ablative proscaenio is used.

Because Latin and English do not always use prepositions in the same way. Latin in + ablative tells you that something happens in/at/on a place, but English chooses the most natural phrase for that noun.

With stage, English normally says on the stage, even though Latin uses in. So the most natural English translation may be on the stage, while the Latin grammar is still completely normal.

Incipit is the 3rd person singular present active indicative of incipio, incipere, meaning to begin.

So incipit means:

• begins
• is beginning (depending on context)

The ending -t is the normal marker for he/she/it in the present tense, so it agrees with the singular subject tragoedia.

Because Latin word order is much more flexible than English word order. Latin uses case endings to show what each word is doing, so it does not depend as heavily on position.

A verb-final order is very common in Latin, so Tragoedia in proscaenio incipit is a very normal sentence pattern.

Yes. Latin could also say:

• In proscaenio tragoedia incipit
• Incipit tragoedia in proscaenio

The basic meaning would stay the same, though the emphasis might shift slightly. Latin speakers often move words around for style, focus, or rhythm.

It could mean either, depending on context. A Latin noun like tragoedia may refer to:

• tragedy as a type of drama
• a tragedy as an individual play

Nothing in this sentence by itself forces only one interpretation. The larger context would make that clearer.