on Thursdays
every Thursday
this Thursday
next Thursday
A: Are you free this week?
A：你这周有空吗？
B: I am only free on Thursdays.
B：我只有在星期四才有空。
1) 星期四（复数）
2) 每逢星期四
1. 星期四
1. The plural form of Thursday, used to indicate something that occurs every Thursday.