Cumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. Often described as "puffy" or "cotton-like" in appearance, cumulus clouds may appear alone, in lines, or in clusters. Cumulus clouds are often precursors of other types of clouds, such as cumulonimbus, when influenced by weather factors such as instability, moisture, and temperature gradient. Cumulonimbus clouds may be associated with phenomena such as landspouts, waterspouts and tornadoes.