As of 2005 the term dependent means either a Qualifying Child or a Qualifying Relative. You are allowed an exemption for each person you claim as a dependent. You can claim an exemption for a dependent even if your dependent files a return. In order to claim an exception for a dependent, you need to satisfy the following conditions:
(a) You cannot claim any dependents if you, or your spouse if filing jointly, could be claimed as a dependent by another taxpayer.
(b) You cannot claim a married person who files a joint return as a dependent unless that joint return is only a claim for refund and there would be no tax liability for either spouse on separate returns.
(c) You cannot claim a person as a dependent unless that person is a U.S. citizen, U.S. resident, U.S. national, or a resident of Canada or Mexico , for some part of the year.
(d) You cannot claim a person as a dependent unless that person is your Qualifying Child or Qualifying Relative.