Explanation:

 The Citizenship Act, 1955, prescribes three ways of losing citizenship whether acquired under the Act or prior to it under the Constitution, viz, renunciation, termination and deprivation:
1. By Renunciation Any citizen of India of full age and capacity can make a declaration renouncing his Indian citizenship.
Further, when a person renounces his Indian citizenship, every minor child of that person also loses Indian citizenship. However, when such a child attains the age of eighteen, he may resume Indian citizenship.
2. By Termination When an Indian citizen voluntarily (consciously, knowingly and without duress, undue influence or compulsion) acquires the citizenship of another country, his Indian citizenship automatically terminates. This provision, however, does not apply during a war in which India is engaged.
3. By Deprivation It is a compulsory termination of Indian citizenship by the Central government.
Note: Naturalisation is the process of attaining the Indian Citizenship.

MNEMONICS:-HUM DIL de chuke SANAM i.e.HUM(We the people of India);DIL(Abe phele Birth or wo Natural process hai);SANAM(Marriage means dual citizenship) rest do by your own.