A cloud which is dependent on a larger cloud system for development and continuance. Roll clouds, shelf clouds, and wall clouds are examples of accessory clouds.

cloud form that is dependent, for its formation and continuation, upon the existence of one of the major cloud genera. It is often an appendage of the parent cloud (as mamma, incus, tuba, arcus), but it also may be an immediately adjacent cloudy mass (as pannus, pileus, velum). See cloud classification.