"Sit on a chair" is the most common way to say "坐在椅子上" in Engpsh.
The phrase "sit on a chair" is a straightforward and pteral way to describe the action of sitting on a chair. It comes from the verb "sit," which means to rest one's body on a surface with the intention of remaining there for a period of time, and the noun "chair," which refers to a piece of furniture with a backrest and a seat, typically with four legs, designed for one person to sit on.
Here are some examples of the phrase "sit on a chair" in context, along with their translations into Chinese:
"Please sit on the chair while I finish setting the table." (请坐在这把椅子上，我马上就把桌子整理好。)
"I prefer to sit on a chair rather than on the floor." (我更喜欢坐在椅子上，而不是坐在地板上。)
"The old man sat on the chair and dozed off." (老人坐在椅子上打起了盹。)