Spayed means a female dog has had her reproductive organs (ovaries and uterus) removed. Neutered means technically that an animal has been de-sexed, but usually is used to refer to a male dog being castrated.
A complement is a word or word group. that completes the meaning of a. verb. Every sentence has a subject. and a verb. Sometimes the subject. and the verb can express a. complete thought all by themselves.
(computing) A bit with the opposite value to the given one; the logical complement of a number. (computing, mathematics) The diminished radix complement of a number; the nines' complement of a decimal number; the ones' complement of a binary number.