Origin of Ortho-, Meta- and Para- Nomenclature

The prefix ortho- comes from the Greek ortho-, meaning “true or correct,” 
The prefix meta- comes from the Greek meta-, meaning “following or after.” 
The prefix para- comes from the Greek para-, meaning “akin to or similar.”

http://www.artsci.uc.edu/chemistry/faculty_staff/jensen/W.%20B.%20Jensen/Reprints/126.%20Othro,%20Meta,%20Para.pdf