This is the 471st most frequent Greek word.
εαυτό
"Εαυτό" means "self" in English.
Here, 'εαυτό' is used in the phrase 'τον εαυτό του' to refer to oneself in reflexive usage.
Ο καθένας πρέπει να αγαπά τον εαυτό του.
Everyone should love themselves.
In this sentence, 'εαυτό' functions in the reflexive construction 'τον εαυτό σου' to indicate the action directed toward oneself.
Πρέπει να προσέχεις τον εαυτό σου.
You must take care of yourself.
The term 'εαυτός' is used here as a noun referring to the concept of one's self or identity.