Self is the complete sense of who you are: your thoughts, feelings, memories, personality, and everything that makes you distinctly you rather than someone else. When you think “I want to try that” or “I don't like spinach” or “I'm good at math,” that inner voice doing the thinking is your self.

Your self includes both parts you can see (like your reflection in a mirror) and parts only you experience directly (like your private thoughts or the way a song makes you feel). It's everything from your sense of humor to your fears, from your memories of last summer to your hopes for next year.

The word appears in dozens of combinations that describe how people relate to themselves: self-confidence means trusting your own abilities, self-control means managing your impulses, and self-doubt means questioning whether you can do something. When someone acts selfishly, they think only of themselves. When they're self-aware, they understand their own strengths and weaknesses.

Philosophers have puzzled over the self for thousands of years: What exactly is it? Where does it come from? Does it stay the same as you grow, or does it change? You might notice that your self feels different at ten than it did at six, as you develop new interests, opinions, and ways of seeing the world.