Learn Polish: Wczoraj nic nie robiłem. - Yesterday I did nothing.

In the Polish past tense, the verb changes depending on who is speaking and their gender. The -ł- part tells us it is in the past, and the -em ending means "I" am the one speaking. Because it uses -łem instead of -łam, we know the speaker is male.

How would a woman say this sentence?

A woman would say Wczoraj nic nie robiłam. The ending -łam is used for the first person singular ("I") when the speaker is female.

Why are there two negative words (nic and nie)?

Polish requires a double negative! In English, we say "I did nothing" or "I didn't do anything." In Polish, if you use a negative word like nic (nothing), you must also put nie (not) in front of the verb. You are literally saying "Yesterday I didn't do nothing."

Why isn't the word for "I" (ja) used in this sentence?

Because the ending of the verb (-em in robiłem) already tells us exactly who did the action ("I"), you don't need to include the pronoun ja. You usually only add it for strong emphasis, like "I did nothing (but my friend did)."