Learn Romanian: Îmi cer scuze că am întârziat.

In Romanian, the expression for apologizing is reflexive: a-și cere scuze (literally, to ask excuses to oneself). Because the subject is I, you must use the dative reflexive pronoun îmi (to myself). Saying just cer scuze without the pronoun sounds incomplete to a native speaker.

Why is că used here instead of pentru (for)?

English uses for followed by an -ing verb (for being late), but Romanian does not use gerunds this way. Instead, expressions of emotion or apology are followed by the conjunction că (that) and a fully conjugated verb. You are literally saying I apologize that I have been late.

Could I use pentru că (because) instead of just că?

While pentru că am întârziat makes logical sense (I apologize because I was late), standard Romanian phrasing strongly prefers just că when connecting an apology to the specific action you are apologizing for.

Is scuze always plural in this expression?

Yes, the set phrase is always a-și cere scuze, using the plural form. Using the singular form scuză would sound unnatural here, as you are asking for excuses in a general, categorical sense.