faithful
faith-ful
adjective
Accurate and true to the original; an exact representation.
"The film is a faithful adaptation."
noun
A loyal supporter or a follower of a religion.
"The faithful gathered for worship."
adjective
Remaining loyal and steadfast to a person, promise, or belief.
"He was a faithful friend."
Thesaurus
Synonyms: true to, fast, truehearted, loyal, firm, true, fold, congregation, close, accurate
Antonyms: unfaithful