According to NOAD conformity is a noun and means compliance with standards, rules, or laws. The same source goes on to state that conformance is another term for conformity. So they are basically the same.
The changes were in conformity with the law.
The changes were in conformance with the law.
However, trawling through Wikipedia reveals that there is a difference between the two when it comes to usage. Here is what it has to say:
Conformance is how well something, such as a product or animal, meets a specified standard and may also refer to:
- Conformance testing, testing to determine whether a product or system meets some specified standard
- SNIA Conformance Testing Program, a program trying to bring third-party standards conformance to the storage networking marketplace
Conformity is the act of matching attitudes, beliefs, and behaviors to group norms. Norms are implicit rules shared by a group of individuals, that guide their interactions with others and among society or social group. This tendency to conform occurs in small groups and/or society as a whole, and may result from subtle unconscious influences, or direct and overt social pressure. Conformity can occur in the presence of others, or when an individual is alone. For example, people tend to follow social norms when eating or watching television, even when alone.