relation比relationship多一层意思亲属家人的意思，其他意思一样，甚至有时候，relationship也可以表示亲属的意思
柯林斯英汉双解大词典
relation?/r?len/?CET4 TEM4?( relations )
1.
N-COUNT?Relations?between people, groups, or countries are contacts between them and the way in which they behave toward each other. 关系
例：
Greece has established full diplomatic relations with Israel.
希腊已经和以色列建立了全面的外交关系。
2.
→ see also?industrial relations,?public relations,?race relations
3.
N-COUNT?If you talk about the?relation?of?one thing?to?another, you are talking about the ways in which they are connected. 关系
例：
It is a question of the relation of ethics to economics.
这是个道德和经济之间关系的问题。
4.
N-COUNT?Your?relations?are the members of your family. 亲属
例：
...visits to friends and relations.
…对亲友的拜访。
5.
PHRASE?You can talk about something?in relation to?something else when you want to compare the size, condition, or position of the two things. 与…相比
例：
The money he'd been ordered to pay was minimal in relation to his salary.
他被要求支付的钱与他的薪水相比是少的。
柯林斯英汉双解大词典
relationship?/r?len?p/?CET4 TEM4?( relationships )
1.
N-COUNT?The?relationship?between two people or groups is the way in which they feel and behave toward each other. 关系
例：
...the friendly relationship between France and Britain.
…英法间的友好关系。
2.
N-COUNT?A?relationship?is a close friendship between two people, especially one involving romantic or sexual feelings. (尤指爱情或性的) 关系
例：
We had been together for two years, but both of us felt the relationship wasn't really going anywhere.
我们在一起已经两年了，但是我们俩都觉得这种关系实在不会有什么结果。
3.
N-COUNT?The?relationship?between two things is the way in which they are connected. 联系
例：
A number of small-scale studies have already indicated that there is a relationship between diet and cancer.
一些小规模的研究已经表明，饮食和癌症之间有一种联系。