The word “authoritative” describes something that is commanding respect and being reliable and official.
One synonym is “influential”. For example, “His opinion is influential and often regarded as authoritative.” This word implies having the power to affect or shape others' thoughts and actions, much like something authoritative.
“reliable” is another option. “The source is reliable and can be considered authoritative.” Reliability gives a sense of trustworthiness and dependability, similar to the quality conveyed by authoritative.
“credible” also works. “The report is credible and has an authoritative tone.” Credibility means being worthy of belief, and an authoritative work is often seen as highly credible.
“definitive” can be used in some contexts. “This book is the definitive guide and is highly authoritative.” It suggests being conclusive and the final word on a subject.
In conclusion, these synonyms for “authoritative” offer different ways to describe something that is respected, reliable, and holds weight in a particular field or situation.