1.preposition[of one variable or unit of measurement x which has a known relationship to another y] Using equivalent expressions in y in place of expressions in x; mapping x to y.
"If x=2y then 5x can be expressed in terms of y as 10y."
2.preposition(by extension) in relation to a particular aspect; with respect to; as regards; concerning; regarding.
"I switched to a different bank for better customer service, but there was little difference in terms of interest rates."