relation
n. C / Un. the way two or more people or things are connected. It can also mean a member of your family.
n. the way in which two or more concepts, objects, or people are connected; a state of being associated. Also used to denote a person related by blood or marriage.
The relation between diet and health is very strong.
Scientists are studying the relation between rising sea temperatures and the frequency of severe storms in the Atlantic.
The diplomat worked tirelessly to improve the relation between the two neighboring countries, focusing on shared economic goals rather than historical grievances.
From Middle English relacion, relacioun, from Anglo-Norman relacioun and Old French relacion (whence French relation), from Latin relātiō, noun of process form from perfect passive participle relātus (“related”), from verb referō (“to refer, to relate”), from prefix re- (“again”) + ferō (“to bear, to carry”). By surface analysis, relate + -ion. Doublet of relazione.
Often used with the preposition 'between' or 'to'. In the sense of a family member, it is a countable noun.
He is a relation of mineHe is a relative of mineWhile 'relation' can mean a family member, 'relative' is the much more common and natural choice for this meaning in modern English.