The terms "minor child" and "unemancipated child" are often used interchangeably, but they do have different legal meanings. The term "minor" according to Black's Law Dictionary means "an infant or person who is under the age of legal competence." In Massachusetts the "age of legal competence" is 18 years of age. So, children are minors only until they turn 18, the age at which they can vote, serve in the military, and take on many of the other rights and obligations of adult civic life.
As any parent knows, however, a child's 18th birthday doesn't magically transform him or her into a self-supporting adult. States, including Massachusetts, recognize that older children may be attending college or otherwise remain dependent on their parents for support -- and this includes child support paid by the noncustodial parent. In short, parents may still be responsible for children who are no longer minors -- that is, they are at least 18 years old -- but are not yet "emancipated" from their parents. And, parents may still owe child support for these children, up to the age of 23.
Under Massachusetts General Laws Chapter 208, Section 28, parents have an ongoing duty to support a child who is at least 18 but not yet 21, if the child maintains a legal domicile with a parent and is principally dependent upon the parent for support. (A domicile is similar to a person's legal residence: Even if a child lives at school, for example, he or she may still be domiciled at home, if that's where the child has a driver's license, is registered to vote, has a permanent mailing address, and intends to return during breaks in the school year, for example.)
Even after a child turns 21 (but before the child turns 23), a parent may be ordered to pay support if the child still maintains a legal domicile with a parent upon whom the child is principally dependent for support because the child is enrolled in an educational program (excluding a graduate program).