This is the 8941st most frequent Spanish word.
tu
"Tu" means "your" (possessive) or "you" (informal subject pronoun).
Here, 'tu' is used as a possessive adjective, meaning 'your', to indicate possession of the book.
¿Es este tu libro?
Is this your book?
In this sentence, 'tú' stands as the subject pronoun, meaning 'you', to indicate the person being addressed.
¿Tú entiendes lo que digo?
Do you understand what I am saying?
In this example, 'tu' functions as a possessive adjective, again meaning 'your', to show ownership of the house.