adjective
loyal
LOY-uhl/ˈlɔɪəl/
Remaining faithful to a person, group, cause, or duty.
The loyal dog remains beside its owner's sickbed instead of leaving for a walk.

Etymology
Loyal shares its origin with legal: faithfulness first meant fulfilling legal obligations and the laws of honor. Allegiance to a ruler broadened into devotion to people, groups, or causes.
In context
The Cardinals were split into factions, the French, the Imperials and a third group loyal to the family of the last Pope.
More examples
- Loyal fans support the team through every losing season.
- He remains loyal to the cause despite growing opposition.
- Our loyal customers keep coming back.
Forms
loyal · more loyal · most loyal
loyalty noun — Faithfulness to someone or something.
loyally adverb — In a faithful and devoted manner.