prescriptive vs. descriptive (adjective) 

In general, prescriptive (pruh-SKRIP-tiv) refers to an action or behavior based on the imposition or enforcement of a rule or method, and descriptive (duh-SKRIP-tiv) refers to an action or behavior based on a norm or standard. As I applied these terms today: Prescriptive linguists argue that “words should be defined as they should be used by intelligent, educated speakers,” while descriptive linguists say that “what matters is whether the word is commonly used, not whether it improves or degrades the language.”