A term is a single mathematical expression. It may be a single number (positive or negative), a single variable ( a letter ), several variables multiplied but never added or subtracted.

Can like terms be negative and positive?

Yes, all positive and negative numbers are like terms.

Are 2x2 and like terms or not like terms?

Summary. Like terms are terms that have exactly the same variable and power in them—whether that's x, x3, y, or even no variable! ... Similarly, 2x and 2x2 wouldn't be like terms because while they have the same variables, the variable is raised to different powers. This can get easily confused with multiplying exponents.