Those that are very thick with moisture do not reflect sunlight as well, and they appear as gray. When nimbo appears in a term as a prefix, or nimbus as the root, then the term refers to a rain-producing cloud. Alto derives from the Latin altus, meaning high, and refers to clouds that appear high in the sky. Cirro, or cirrus, means curl of hair in Latin. This term refers to a wispy, curly formation.
Cumulus derives from the Latin word for heap.
Cumulus clouds are piled and fluffy. Stratus derives from the Latin verb sternere, which means to stretch. Stratus clouds extend in flatter formations than cumulus ones. Your kids might enjoy keeping a record of the types of clouds they observe on different days and noting the weather conditions associated with them.