Spay and neuter are related to animals and their reproductive system. Neuter can refer to a female or male animal, that has had their reproductive system removed. Spay can only be used to refer to a female that has had their reproductive system removed. While they are in common for the purpose of controlling births, neuter has more purposes and advantages. A neuter helps with increasing the amount of work that the animal is able to do and help with controlling aggression. With spray, the condition is spraying. With neutering, the condition is called castration and the testicles are removed.