adjective
devout
dih-VOWT/dɪˈvaʊt/
Deeply and sincerely committed, especially to a religious faith.
Her devout faith guides the way she treats other people.

Etymology
The vow root lies behind the description “given up by vow.” This became religious dedication and piety, with sincerity and solemn commitment extending the meaning beyond worship.
In context
He became intensely devout, but his piety was partly a retreat from the political demands he couldn't meet.
More examples
- He remains a devout Catholic even when life is difficult.
- As a devout Muslim, she sets aside time for prayer.
- A devout pacifist, he opposes every form of armed conflict.
Forms
devout · devouter · devoutest
devoutly adverb — With deep religious commitment or sincerity.
devoutness noun — The quality of being deeply religious or committed.