A dependent is someone who is unable to care for or support themselves and looks for such care and/or support from another. Under the tax rules of the Internal Revenue service, a person may claim a tax exemption for a dependent who has a certain relationship to the taxpayer, such as a son or daughter, brother or sister, mother or father, etc., or who makes the taxpayer's household his or her primary residence.
A person qualifying as your dependent generally may be your child, stepchild, adopted child, grand child, great-grand child, son or daughter in law, father or mother in law, brother or sister in law, parent, brother, sister, grand parent, step-parent, stepbrother or sister, half brother or sister, and, if related by blood, uncle, aunt, niece, or nephew. The above relatives do not have to live with you.
Also, any person, whether or not you are related to them, who is a member of your household for the entire tax year, except for temporary absences; must receive less than a statutorily defined amount of gross income, unless the dependent is your child and either under age 19 or a full-time student under age 24; must receive more than one-half of his or her support from you; cannot file a joint tax return with his or her spouse, unless the joint tax return is filed solely to obtain a tax refund when neither the child nor the spouse is required to file a tax return; and must be a U.S. citizen or national, or a resident of the U.S., Canada, or Mexico.
The following is an example of a federal statute defining the term Dependent:
According to 37 USCS § 401(a) [ Title 37. Pay and Allowances of the Uniformed Services; Chapter 7. Allowances] the term "dependent", with respect to a member of a uniformed service, means “the following persons:
(1) The spouse of the member.
(2) An unmarried child of the member who--
(A) is under 21 years of age;
(B) is incapable of self-support because of mental or physical incapacity and is in fact dependent on the member for more than one-half of the child's support; or
(C) is under 23 years of age, is enrolled in a full-time course of study in an institution of higher education approved by the Secretary concerned for purposes of this subparagraph, and is in fact dependent on the member for more than one-half of the child's support.
(3) A parent of the member if--
(A) the parent is in fact dependent on the member for more than one-half of the parent's support;
(B) the parent has been so dependent for a period prescribed by the Secretary concerned or became so dependent due to a change of circumstances arising after the member entered on active duty; and
(C) the dependency of the parent on the member is determined on the basis of an affidavit submitted by the parent and any other evidence required under regulations prescribed by the Secretary concerned.
(4) An unmarried person who--
(A) is placed in the legal custody of the member as a result of an order of a court of competent jurisdiction in the United States (or Puerto Rico or a possession of the United States) for a period of at least 12 consecutive months;
(i) has not attained the age of 21;
(ii) has not attained the age of 23 years and is enrolled in a full time course of study at an institution of higher learning approved by the Secretary concerned; or
(iii) is incapable of self support because of a mental or physical incapacity that occurred while the person was considered a dependent of the member or former member under this paragraph pursuant to clause (i) or (ii);
(C) is dependent on the member for over one-half of the person's support;
(D) resides with the member unless separated by the necessity of military service or to receive institutional care as a result of disability or incapacitation or under such other circumstances as the Secretary concerned may by regulation prescribe; and
(E) is not a dependent of a member under any other paragraph.”