In linguistics, inalienable possession (abbreviated INAL) is a type of possession in which a noun is obligatorily possessed by its possessor. Nouns or nominal affixes in an inalienable possession relationship cannot exist independently or be "alienated" from their possessor. For example, a hand implies "(someone's) hand", even if it is severed from the whole body. Likewise, a father implies "(someone's) father". Inalienable nouns include body parts (e.g. leg, which is necessarily "someone's leg"), kinship terms (e.g. mother), and part-whole relations (e.g. top). Many languages reflect this distinction, but they vary in the way they mark inalienable possession. Cross-linguistically, inalienability correlates with many morphological, syntactic, and semantic properties.
In general, the alienable–inalienable distinction is an example of a binary possessive class system, i.e., a language in which two kinds of possession are distinguished (alienable and inalienable). The alienability distinction is the most common kind of binary possessive class system, but it is not the only one. Some languages have more than two possessive classes: the Anêm language of Papua New Guinea, for example, has at least 20.
Statistically, 15–20% of the world's languages have obligatory possession.
The following real-world relationships often fall under inalienable possession:
Other things, such as most objects, may or may not be possessed. When these types of objects are possessed, the possession is alienable. Alienable possession is generally used for tangible items which one might cease to own at some point (e.g. my money) whereas inalienable possession refers to a perpetual relationship which cannot be readily severed (e.g. my mother).