Civic, civil, civilian are not close synonyms but rather words whose meanings lend themselves to confusion. In a sense they have a common meaning: of, relating to, or characteristic of a citizen —but in each case the word citizen has a specific or particular meaning.
Civic implies some relation to a city and its citizens; city, however, is used loosely so as to cover any community having closely related interests (as a town, a village, or a city proper) or any municipality or corporation having powers of local self-government: in this sense civic is used in distinction from state, federal, and national.
Often the word comes close in meaning to public when used to modify acts, functions, obligations, or qualities, the chief distinction consisting in its closer application to the life of the community.
Civil, in general, has reference to a citizen as a member of the state, or to citizens as members of the state. In this sense state denotes usually a larger organized unit than that denoted by city and comes close in meaning to country, nation, and people.
The term civil implies reference to this organization; thus, civil liberty is the liberty permitted to a citizen by the laws of the state or exemption from arbitrary government interference; a civil war (as opposed to a foreign war) is a conflict between citizens of the same state.
More specifically, there is often a definitely implied contrast in the use of civil; the civil authorities are those that prevail in all affairs except where ecclesiastical authorities or military authorities have the final say; civil service denotes service of the state in any capacity that does not distinctively belong to the military organization; thus, civil architecture applies to architecture which is neither ecclesiastical nor military; in law, civil actions are distinguished from criminal actions as relating to proceedings in connection with the private or individual rights of citizens; also, in law, a civil death implies not a natural (that is, actual) death, but the loss or renunciation of all legal rights or status.
Civilian refers to persons who are not members of the armed forces and is used chiefly in contrast to military.