It's used in respect for talking to a superior and respectfully, so is there even an english equivalent for it or is it just a special title used for Chinese?
I believe there is no English equivalent, but there are some equivalents that I know of.
- older/younger in age or higher/lower in rank.
Bob is the senior developer in our team.
James is 5 years my junior.
Being a senior, I shall take the duty.
- person who has a job/position prior to another.
Larry, the new coach of Mickey (I made this up), is way more experienced than his predecessors.
Note the subtle difference between predecessor and senior – predecessor has to be someone that pre-existed in the setting, whereas senior is someone that co-exists in the setting.