When asked what the fundamental, or essential, principles of life are, a teenager might reply, "Breathe. Be a good friend. Eat chocolate. Get gas money."
Fundamental has its roots in the Latin word fundamentum, which means "foundation." So if something is fundamental, it is a key point or underlying issue — the foundation, if you will — that the thing is built upon. Teachers argue that math fundamentals include memorizing the times tables and understanding long division. Many people would also argue that math fundamentals should include knowing how to use a calculator and knowing where the calculator's extra batteries are kept.