This is the 3051st most frequent Polish word.
podpisał
"Podpisał" means "he signed" in English.
This sentence illustrates a simple past action using the verb "podpisał" to indicate that Jan completed the action of signing.
Jan podpisał dokument.
Jan signed the document.
Here, "podpisał" is used in a question to inquire whether the professor completed the signing of the letter, again reflecting a past action.
Czy profesor podpisał list rekomendacyjny?
Did the professor sign the recommendation letter?
In this sentence, "podpisał" is used to describe the act of signing, with "się" emphasizing that the subject is performing the action upon themselves in context with ownership or responsibility.