precursor

 
Pronunciation: /prɪˈkəːsə/

noun

  • a person or thing that comes before another of the same kind; a forerunner: a three-stringed precursor of the violin
  • a substance from which another is formed, especially by metabolic reaction: pepsinogen is the inactive precursor of pepsin

Origin:

late Middle English: from Latin praecursor, from praecurs- 'preceded', from praecurrere, from prae 'beforehand' + currere 'to run'

Spelling help

The ending of precursor is spelled -or.