Plant milk is a general term for any milk-like product that is derived from a plant source. There is no formal or legal definition for plant milk. The most popular variety is soy milk.
There are a variety of reasons for consuming plant milk including lactose intolerance and milk allergy, religious/spiritual reasons, simple taste preference, veganism and ovo-vegetarianism, and health conditions such as PKU—a rare genetic disorder requiring a low-phenylalanine diet—that makes digestion of animal proteins, especially casein found in dairy, difficult or impossible. After soy, rice and almond milk are the most common non-dairy milks in the USA, oat milk is the second most common plant milk in Europe, sold even in average supermarkets (as opposed to almond milk, which is usually more expensive, and is only found in health food stores). There is also coconut milk, hazelnut milk and milk from peas and lupin.