pre·scrip·tive 
(prĭ-skrĭptĭv)
(prĭ-skrĭptĭv)adj.
1.
a. Relating to or making rules, laws, or directions: prescriptive pronouncements.
b. Linguistics Based on or establishing norms or rules indicating how a language should or should not be used rather than describing the ways in which a language is used.
2. Law Of or relating to acquisition or occupancy by prescription.
3. Archaic Sanctioned or authorized by long-standing custom or usage.
pre·scriptive·ly adv.
pre·scriptive·ness n.