The list of cloud types classifies the tropospheric genera as high (cirrus, cirrocumulus, cirrostratus), middle (altocumulus, altostratus), multi-level (nimbostratus, cumulus, cumulonimbus), and low (stratocumulus, stratus) according to the altitude level or levels at which each cloud is normally found. Small cumulus are commonly grouped with the low clouds because they do not show significant vertical extent. Of the multi-level genus-types, those with the greatest convective activity are often grouped separately as towering vertical. The genus types all have Latin names.

The genera are also grouped into five physical forms. These are, in approximate ascending order of instability or convective activity: stratiform sheets; cirriform wisps and patches; stratocumuliform patches, rolls, and ripples; cumuliform heaps, and cumulonimbiform towers that often have complex structures. Most genera are divided into species with Latin names, some of which are common to more than one genus. Most genera and species can be subdivided into varieties, also with Latin names, some of which are common to more than one genus or species. The essentials of the modern nomenclature system for tropospheric clouds were proposed by Luke Howard, a British manufacturing chemist and an amateur meteorologist with broad interests in science, in an 1802 presentation to the Askesian Society. Very low stratiform cloud that touches the Earth's surface is given the common name, fog, which isn't included with the Latin nommenclature of clouds that form aloft in the troposphere.

Above the troposphere, stratospheric and mesospheric clouds have their own classifications with common names for the major types and alpha-numeric nomenclature for the subtypes. They are characterized by altitude as very high (polar stratospheric] and extreme level (noctilucent) and are both generally cirriform in structure.