to assign constituent structure to (a sentence or the words in a sentence)
2.
(intr) (of a word or linguistic element) to play a specified role in the structure of a sentence
3.
computing to analyse the course code of a computer program to make sure that it is structurally correct before it is compiled and turned into machine code
[C16: from Latin pars (orātionis) part (of speech)]
c.1553, "to state the parts of speech in a sentence," verb use of M.E. pars (n.) "part of speech" (c.1300), from O.Fr. pars, pl. of part "part," from L. pars (see part (n.)) in school question, Quae pars orationis? "What part of speech?"