The friend who doesn't know any of your other friends
We like integration. We like killing two birds with one stone by catching up with several groups of friends at once. But there are times when you need to make an S.O.S call to a friend who is completely uninvolved and removed from a situation who can offer objective advice so it a bonus that your friendship exists without orbiting around your other ones.
There is a level of privacy to this friendship that doesn't exist in friendship circles. It will be easier to share some of your hopes and dreams, fears and concerns knowing that they are not going to be discussed when you're not around.
catch up with 追上； 赶上； 和…算旧账； 使…最终尝到苦果
Most late developers will catch up with their friends.
She used the day to catch up with administrative tasks.
He stopped and let her catch up with him.