authoritative vs imperative

authoritative

adj
  • Having a commanding style. 

  • Arising or originating from a figure of authority 

  • Highly accurate or definitive; treated or worthy of treatment as a scholarly authority 

imperative

adj
  • Expressing a command; authoritatively or absolutely directive. 

  • Having semantics that incorporates mutable variables. 

  • Essential; crucial; extremely important. 

  • Of, or relating to the imperative mood. 

noun
  • A verb in imperative mood. 

  • The grammatical mood expressing an order (see jussive). In English, the imperative form of a verb is the same as that of the bare infinitive. 

  • An essential action, a must: something which is imperative. 

How often have the words authoritative and imperative occurred in a corpus of books? (source: Google Ngram Viewer )