So, let me see if I'm still on the same page:
Legally, an adult is defined as a person who has entered the age of majority and is able to enter into contracts. They are legally responsible now in the sense that they can act in their own accord and are not subject to parental rights any longer.
In South Africa, the legal age is 18, as per the Children's Act of 2005.
A legal entity is a non-living organisation that derives legal rights - for example a body corporate or a company.
Emancipation is a little vague for me: the right to be declared free to make one's own decisions? I could use some clarity there.