What are exemptions? does my child count as one if they lived with other parent for more that 6 mos?

[Hal_Al]

An exemption is the deduction ($4050) that your get for claiming someone as a dependent. If you do not meet the rules for claiming someone as a dependent, you do not get the $4050 exemption from taxation. 

No, you cannot claim a child's exemption if he lived with the other parent. The custodial parent has first priority on claiming the children on her taxes; regardless of the amount of support provided by the non-custodial parent. The non-custodial parent can only claim the child's exemption (claim the child  as a dependent) if the custodial parent gives permission (on form 8332) or if it's spelled out in a pre 2009 divorce decree. 

[freedom1]

Ok, we filled out the 8332 for him to claim the EIC and tax credit, so I guess I can only myself as one exemption. We have been seapted and living apart for 3 years, but not legally divorced, so I am amending a return and filing married filing separately.

[Hal_Al]

He is not allowed to claim EIC. The form 8332 allows him to claim the child's exemption and the child tax credit.

 There is a special rule in the case of divorced & separated (including never married) parents. When the non-custodial parent is claiming the child as a dependent/exemption/child tax credit; the custodial parent is still allowed to claim the same child for Earned Income Credit, Head of Household filing status, and day care credit. This "splitting of the child" is not available to parents who lived together at any time during the last 6 months of the year; then only one of you can claim the child for any tax reasons. The tax benefits may not be split in any other manner.

Note in particular that the non-custodial parent can never claim the Earned Income Credit, Head of Household filing status or the day care credit, based on that child, even when the custodial parent has released the exemption to him.
 So, it's good idea to let the other parent know that you will be claiming those items, as many first time divorced parents are not aware of this rule and may try to claim those items, which will cause the IRS to send out letters.
Ref: <a rel="nofollow" target="_blank" href="http://www.irs.gov/publications/p17/ch03.html#en_US_2014_publink1000170897">http://www.irs.gov/publi...> Scroll down to "Children of divorced or separated parents (or parents who live apart)"