Opacus

Clouds : classification
Genera Cirrus Ci Cirrocumulus Cc Cirrostratus Cs Altocumulus Ac Altostratus As Stratocumulus Sc Stratus St. Cumulus Cu Nimbostratus Ns Cumulonimbus Cb	species calvus cal capillatus cap castellanus cas congestus con fibratus fib floccus flo fractus fra humilis hum lenticularis len mediocris med nebulosus neb spissatus spi stratiformis st uncinus unc volutus vol	Subspecies duplicatus you intortus in lacunosus la opacus op perlucidus pe radiatus ra translucidus tr undulatus un vertebratus ve Special forms arcus arc asperitas asp cauda cau cavum cav fluctus flu flumen flm incus inc mamma mam murus mur pannus pan pileus pil praecipitatio pra tuba tub velum vel virga vir

Opacus (op) ( lat. "Dark, rich in shadows ") are clouds in extensive spots, fields or layers, which are mostly so opaque that the sun or moon are completely covered. This subspecies is mutually exclusive with Translucidus .

The name is used for Altocumulus , Altostratus , Stratocumulus and Stratus .

• 

  Stratocumulus stratiformis opacus, dense layer of cloud