These words have many meanings in different contexts, but here are some distinctions related to the core ideas of “important” and “easy.” 1. Fundamental = part of the intellectual foundation of some subject.. Example: “The fundamental principles of quantum physics.” Fundamental does not mean “easy” or “simple.” 2. Essential = something that is necessary, and without which a thing cannot exist or is impossible. Example: “Freedom of the press is essential to a healthy democracy.” 3. Basic = simple, uncomplicated, or at a low level of skill. Example: “He has only basic language skills in Spanish.” “He understands the basic rules of chess, but does not understand the finer points of strategy.” 4. Primary = of first or highest importance. Example: “The primary reason that I went to medical school is that I like to help people. A secondary reason is that I wanted a high salary.” 5. Elementary = simple/easy. Example: “Addition and subtraction are elementary math.”