Accretion may refer to:

• Accretion (finance), predictable changes in the price of certain securities
• Accretion (geology), an increase of land by the deposit of waterborne sediment
• Accretion (science), increase in size by gradual addition of smaller parts
• Raindrop accretion, in meteorology, is the process by which water vapor in clouds forms water droplets around nucleation sites, then falls to the surface as precipitation. A similar process occurs during the formation of snowflakes, when the air temperature is below the freezing point of fresh water.

Accrétion