Cloud Definitions
Invisible water vapor condenses to form visible clouds of liquid water droplets.
- en.m.wikipedia.org/wiki/Water_vapor

The droplets are so small and light that they can float in the air.
- www.weatherwizkids.com/weather-cloud

A visible mass of liquid droplets or frozen crystals... 
suspended in the atmosphere above the surface of a planetary body.
-  en.wikipedia.org/wiki/Cloud

Cloud genera, species, and varieties

Stratus
Stratus nebulosus
Stratus nebulosus translucidus
Stratus nebulosus translucidus undulatus
Stratus nebulosus opacus undulatus
Stratus nebulosus opacus
Stratus fractus
Stratus cumulogenitus
Stratus nimbostratogenitus
Stratus cumulonimbogenitus
Stratus stratocumulomutatus
Stratocumulus stratomutatus
Stratocumulus altocumulomutatus
Stratocumulus nimbostratomutatus
Stratocumulus lenticularis
Stratocumulus lenticularis undulatus
Stratocumulus lenticularis duplicatus
Stratocumulus castellanus
Stratocumulus castellanus lacunosus
Stratocumulus stratiformis
Stratocumulus stratiformis translucidus
Stratocumulus stratiformis translucidus
undulatus
Stratocumulus stratiformis translucidus
duplicatus
Stratocumulus stratiformis translucidus radiatus
Stratocumulus stratiformis perlucidus
Stratocumulus stratiformis perlucidus radiatus
Stratocumulus stratiformis perlucidus undulatus
Stratocumulus stratiformis perlucidus duplicatus
Stratocumulus stratiformis opacus
Stratocumulus stratiformis opacus undulatus
Cumulus
Cumulus fractus
Cumulus humilis
Cumulus humilis radiatus