What are all the parts of an algebraic expression and can you define them?

Variables - a quantity that may change, depends on the context of the math problem.  Ex: x,y
Terms - a variable, or constant, that is multiplied by a variable or variables.
Ex: 5x + 2 + 3y <-- has 3 terms
Coefficient - the constant that multiplies the variable and is next to a variable, Ex: (5x) <-- coefficient is 5
Constants - A fixed value such as 5, 6, 7, etc