authoritative
adjective /ɔːˈθɒrətətɪv/
  /əˈθɔːrəteɪtɪv/
- showing that you expect people to obey and respect you
- an authoritative tone of voice
 
Extra Examples- A very authoritative voice shouted, ‘Get back inside.’
 - His tone was clear and authoritative.
 - She began to resent his authoritative manner.
 
 - that you can trust and respect as true and correct
- the most authoritative book on the subject