This is the 7771st most frequent Spanish word.
mi
"Mi" means "my" in English.
In this sentence, 'mi' is again a possessive adjective showing ownership of the backpack.
¿Dónde está mi mochila?
Where is my backpack?
Here, 'mi' indicates possession, specifying which friend is being referenced.
Mi amigo siempre llega temprano.
My friend always arrives early.
Here, 'mi' is a possessive adjective referring to the speaker's favorite item.