Relation (noun)

1. The way in which two or more concepts, objects, or people are connected, or the state of being connected.
2. The connection or association between people, such as family or friends.
3. The connection or association between events or situations.
4. The connection or similarity between different things.
5. A person who is connected to another person, especially by family ties.

Origin:

From middle english relacioun, from old french relacion, from latin relātiō ("a bringing back, a referring, a relation"), from relātus, perfect passive participle of relātō ("bring back, refer"), from re- + latus ("borne, carrie.d")

Examples:

1. He's studying the relation between diet and health.
2. She has a good relation with her sister.
3. The relation between cause and effect is important.
4. The relation between the two theories is not clear.
5. She's a distant relation of mine.