Meaning of equivalent

(adj) being essentially equal to something; "it was as good as gold"; "a wish that was equivalent to a command"; "his statement was tantamount to an admission of guilt"

(noun) a person or thing equal to another in value or measure or force or effect or significance etc; "send two dollars or the equivalent in stamps"

the atomic weight of an element that has the same combining capacity as a given weight of another element; the standard is 8 for oxygen