"Line of research" or "research line"? [closed]

Which one is more appropriate in USA English? "Line of research" or "research line"?

Also, if there are individual "lines of research" for each person, is it correct to say:

Everyone's line of research

or should I say:

Everyone's lines of research

"Line of research" is a much more familiar term. "Research line" would likely mean something different, such as a product line that exists for doing research, or such as the viewpoint someone is taking in their research.

Yes, there can be multiple lines of research. One organization might have several, and even an individual researcher could have several lines of research. "Everyone's line of research" can refer to one more multiple lines of research; this isn't specific to lines of research, the same sort of ambiguity would exist if we were talking about everyone's bicycle or everyone's table.