Altocumulus clouds are rounded puffs of cloud larger than cirrocumulus. Altostratus clouds cover the sky with a grayish veil through which the sun or moon may shine as a spot of pale light. Nimbostratus clouds are thick, dark, and shapeless and usually bring rain or snow. Stratocumulus clouds are large and lumpy, round or rolled-looking, and often cover the entire sky. Stratus clouds are generally dark and appear as streaks across the sky or as a gray layer hanging above the Earth.
Stratus clouds are generally shapeless.
The various genera, or types, of cloud often merge, making it very difficult to identify a particular cloud formation.