re·la·tion 
/rɪˈleɪʃən/ noun
plural re·la·tions /rɪˈleɪʃən/ noun 1 relations [plural] a : the way in which two or more people, groups, countries, etc., talk to, behave toward, and deal with each other
▪ The incident led to tense international relations. — see also industrial relations
b formal : sexual intercourse
▪ sexual relations outside of marriage 2 : the way in which two or more people or things are connected [count] ▪ the relations [=(more commonly) relationships] between weather events and erosion [noncount] ▪ This movie bears no relation to the book by the same title. [=it is not connected to the book at all; the movie and the book do not tell the same story, have the same characters, etc.] 3 : a person who is a member of your family [count] ▪ We threw a big party for all our friends and relations. [=relatives] ▪ Is he a relation of yours? [=are you related to him?] [noncount] ▪ I'm Jill Jones, and this is Mike Jones—no relation. [=we have the same last name but we are not related; we are not members of the same family]
▪ The incident led to tense international relations. — see also industrial relations
b formal : sexual intercourse
▪ sexual relations outside of marriage
in relation to
formal 1 — used to talk about what something is like by comparing it to something else or by seeing how it is related to something else ▪ The monkey's eyes are large in relation to its head. ▪ understanding literature in relation to history 2 : about (something or someone)
▪ I have several comments to make in relation to [=in/with reference to, regarding] the subject at hand.
▪ I have several comments to make in relation to [=in/with reference to, regarding] the subject at hand.
