Trenul este rapid și ajunge la aeroport la timp.

In Romanian, the definite article for masculine and neuter nouns is attached to the end of the word.

• tren = “train” (indefinite)
• trenul = “the train” (definite)

This suffixed article replaces the separate “the” you’d use in English.

Both este and e mean “is.”

• este is the full form, slightly more formal or used in writing.
• e is the colloquial contraction common in speech.

You can say Trenul e rapid in conversation, but Trenul este rapid is more standard.

Adjectives in Romanian agree in gender and number with the noun they describe.

• trenul is masculine singular.
• The masculine singular form of the adjective is rapid.
  If the noun were feminine (for example, mașina “the car”), you’d say mașina este rapidă.

ajunge is the 3rd person singular present indicative of the verb a ajunge (“to arrive/reach”).

• eu ajung = I arrive
• tu ajungi = you arrive
• el/ea ajunge = he/she arrives

So ajunge here means “it arrives” or “it reaches.”

The preposition la means “to” or “at,” and it’s used with a ajunge to mark the destination:

• ajunge la aeroport = “arrives at (the) airport.”

Here aeroport remains indefinite, so there’s no added article.

When using ajunge la + [place], Romanian often omits the definite article for generic or unspecified places.

• ajunge la aeroport = “arrives at an airport” or “arrives at the airport” in a general sense.
  If you wanted to emphasize a specific airport already mentioned, you could say ajunge la aeroportul.

la timp is the fixed expression for “on time” (i.e., not late).

• ajunge la timp = “arrives on time.”
  By contrast, în timp means “in time” as in “before a deadline” or “with enough time to spare.” They are not interchangeable in this context.