Something that can be used in place of milk. The most common reason to use a milk substitute is because of lactose intolerance. A person might also be trying to avoid using products that exploit animals; here I refer to products that are free of animal byproducts as 'Vegan'. Most of these may, depending on the manufacturer, contain gluten. None of these taste much like cow milk, but may be quite a bit better than nothing.
Coconut milk: 1/2 canned coconut milk, 1/2 water, adjust to taste. Vegan. Can be used in many recipes that call for milk. Lactose free.
Soy milk: some people are allergic to this. Vegan. Can be used for cooking and possibly for weird tasting cereal. Lactose free.
Nut milk: Some people are allergic to this. Vegan. Can be used for cooking. Very different on cereal. Lactose free.
Rice milk: Vegan. Can be used for cooking and cereal. Lactose free.
Oat Milk: Can be used for cooking and cereal. Usually Vegan (may use honey as sweetener). Lactose free.
Potato milk: May not work for cooking. Appears to be Vegan. Lactose free.
Goat Milk: Does not contain the allergenic casein protein alpha-S1. Has slightly less lactose than cow milk, but not enough to make much of a difference. May be used for cooking and possibly on cereal.
Human Milk: Extremely healthy; recommended for all children for at least the first 6 months of life. Considered Vegan. No other milk-like substance should be used to replace this, with the possible exception of baby formula.