What is the terminology in International law for a person who is a citizen by birth?
The phrases 'citizen by birth' and 'citizen by blood' have similar meanings. A citizen by birth is usually a person who is either born in the U.S., its territories or military bases and may refer to persons born overseas to Americans. A person born in the U.S. may also be considered a citizen by 'right of the soil.' A person born to Americans overseas may also be considered a 'citizen by law' or 'a naturalized citizen.'
A citizen by blood (or by 'right of the blood') typically refers to a person born to a parent or parents who are U.S. citizens.