To release from slavery, to free.
To grant citizenship to someone not born a citizen.
To make (a word) a natural part of the language, using the native homologue of each phoneme (and often for each morpheme) of the imported word (e.g., native inflections).
To study nature.
To limit explanations of a phenomenon to naturalistic ones and exclude supernatural ones.
To acclimatize an animal or plant.
To make natural