Tu eres means you are, but I've never heard of the word nansi is spanish. (I'm not a native speaker.) There is a similar word though, ansi, and the verb form of it is así, which means obsolete.
loca tu eres means 'You're crazy'
"Tu eres gordo" means "you are fat" in Spanish.
tu eres linda tambien means you are beautiful, too
"Tu eres mi mundo" in English means "You are my world."
Tu eres mi amor means: You are my love
"Tu eres linda" means "you are beautiful" in English.
It means, "You're my heart, you're my love, you're my life."
As a question (¿eres tu maría?) literally means "are you you maria?" = "is that you maría?" in english NO IT MEANS " ARE U MARIA "
Tu eres muy lista in English means you're so clever.
COMO ERES TÚ --- The way you are
It means "you are".