I have 3 groups of colleagues in terms of affinity.
The first group makes up the people I hit it off with. I have lunch on a regular basis with them and know their private background stories.
I feel comfortable having conversation with them.
In the second group, there are those who I have just small talks with, but don't eat together. I don't have much information on their private life.
The last group has two people who I really dislike but manage to just say hello in the morning though.
Almost every worker may have this kind of different degree of affinity with their colleagues.
But even the people of the first group, I never hang out with them off the office. They are all married women with children.
I don't want to be mistakable haha. Actually, even though I feel close to them, I try not to be loose a lot. Because mistakes between man and woman can necessarily happen in a too comfortable relationship. A good relationship can be kept in a mutual respect.