Drizzle is defined as liquid drops of precipitation less than 0.02 inches in diameter falling close together, whereas rain is liquid precipitation of greater diameter and spaced further apart. Drizzle falls in amounts of less than 0.03 inches per hour and rain comes down at a rate of 0.04 inches per hour or more.
Drizzle comes from thinner stratus clouds that are lower to the ground. Stratus clouds cannot hold heavier rain drops because air currents are weak. Rain develops inside cumulus clouds and can get up to 0.25 inches wide before falling out of the sky. Cumulus clouds are thicker and more stable and contain larger drops.
Both rain and drizzle fall to the ground and come in different intensities known as light, moderate and heavy. Light drizzle rarely hinders visibility. Heavy drizzle reduces visibility to a quarter of a mile or less. Light rain falls at 0.10 inches per hour or less. Heavy rain is more than 0.30 inches of precipitation in 60 minutes.
Other types of liquid precipitation such as fog stay suspended in the air without landing on the ground. Rain falls in the form of showers that can be sporadic or heavy. Colloquial terms for precipitation include soakers and sprinkles when describing heavy or light rain.