【Inhabitant】 , 【denizen】 ,  【resident】 ,  【citizen】  are comparable when meaning one whose home or dwelling place is in a definite location.

【Inhabitant】 , the least specific word, implies nothing more than an abode in a given place.

【Denizen】 denotes one that belongs by birth or naturalization to a given locality. Even when substituted in literary use for  【inhabitant】 , 【denizen】 retains something of its own flavor of belonging to the locality by birth or naturalization.

【Resident】  is not always clearly distinguished from  【inhabitant】 , especially when a town or city, as distinguished from a state or country, is in question. Often the term implies nothing more than tenancy of a room, an apartment, a house, or a locality for a considerable length of time.

Often, in the case of a person who has several residences or who lives mainly in a place other than the one regarded as his home, the term suggests not permanent inhabitancy but legal recognition of one of these places as his domicile, and as the seat of his fundamental legal rights (as of voting) and responsibilities (as of paying income tax).

In reference to a country,  【resident】  is more usual than  【inhabitant】 as a designation of an alien living in that country for a time and regarded as subject to certain taxes.

【Citizen】  when denoting a person that is an 【inhabitant】 is rarely wholly free from its political sense (see  【CITIZEN】 2 ); hence, it usually carries some suggestion of membership in, as distinct from mere presence in, a community and of possession of the privileges and obligations inherent in such membership. It is particularly applicable to an adult and substantial 【resident】 of a city or town.