Wiktionary
a. In equal parts; half adv. In two equal parts. n. 1 Half one thing and half another. 2 (context US English) A mixture of cream and milk often used in coffee, defined by the US Food and Drug Administration to contain between 10.5% and 18% milk fat. 3 A mixture of two alcoholic beverages, most frequently those brew#Verb from malt, such as porter and ale or mild and bitter beers, in about equal parts; also used for equal parts of an alcoholic beverage and water. 4 A person of mixed race or with dual nationality. 5 (context British English) A combination of both rice and chips as an accompaniment to a curry, as opposed to one or the other. 6 (context UK English) A combination of beer and ale (or similar alcoholic drinks) in equal quantities. 7 Both oral sex and vaginal sex performed in sequence by a prostitute 8 (label en US) A mixture of half lemonade and half iced tea.
Wikipedia
Half and half refers to various beverages or liquid foods made of an equal-parts mixture of two substances, including dairy products, alcoholic beverages, and soft drinks.
Usage examples of "half and half".
The men wanted to take only girls, while the women wished only boys, so that the compromise of half and half pleased no one but did have certain sense to commend it.