authoritative

authoritative /əˈθorəˌteɪtɪv/ adjective
authoritative
/əˈθorəˌteɪtɪv/
adjective
Britannica Dictionary definition of AUTHORITATIVE
[more authoritative; most authoritative]
1 
: having or showing impressive knowledge about a subject
2 
: having the confident quality of someone who is respected or obeyed by other people

— authoritatively

adverb