piano
In Italian, 'piano' is used both as a musical instrument, same as in English, and also to mean 'slowly'. For instance, 'piano piano' means slowly slowly. This can vary based on context of the conversation.
Speak more slowly, please.
In this context, 'piano' is an adverb modifying 'parla', which means 'speak'. It's asking someone to slow down their speed of speech.
My plan for the weekend is to relax at home.
Here, 'piano' is a noun meaning 'plan'. It's indicating what the speaker intends to do over the weekend.
I was playing the piano.
In this sentence, 'piano' is the name of a musical instrument, a piano, that the speaker had been playing.