In American English, “dependant” is a rare alternative spelling of “dependent,” which means “relying on someone or something else for aid, support” or “a person who is financially supported by someone else.” However, British English treats “dependant” as a noun form of “dependent” and differentiates these two words. In British English, “dependant” means “a person who depends on another person, organization, etc, for support, aid, or sustenance, especially financial support”.
The British English “dependant” or the American English “dependent” is a legal term that indicates a person who is unable to care for or support themselves and looks for such care and/or support from another person or organization. This may qualify the party supporting the dependent for an exemption to reduce their income taxes. For example, a dependent of a person may be their child, adopted child, parents, brother, sister and so others.
As an alternative spelling of "dependent", the American English "dependant" has no definition of its own. The word can be used as either an adjective or a noun. However, in British English, "dependant" should not be confused with "dependent." The British English "dependant" is considered to be the only correct spelling of the noun, and "dependent" is a variant. Yet the variant "dependent" is now standard, and is used as commonly as the correct form "dependant."