Like terms

Terms with exactly the same variable part, including the same indices; for example, $3x^2$ and $-7x^2$ are like terms.

Terms that have exactly the same variable part, including the same powers, and can therefore be collected.

Terms with identical variable and index parts, or surd terms with the same simplified root part.

Terms with the same algebraic or irrational-symbol part, including the same variables and powers or the same surd or power of $\pi$; only their numerical coefficients may differ.

Terms containing exactly the same variables raised to the same powers.

Terms with exactly the same variables raised to the same powers, such as $3x^2$ and $-7x^2$.