na-adjective
devoted; self-sacrificing; dedicated
Describes wholehearted dedication to a person, cause, or task, often implying putting others' needs before one's own. Commonly used with な to modify nouns.
彼女は献身的な看護師として知られている。
She is known as a devoted nurse.
彼の献身
His dedicated efforts led the project to success.
忠実 means faithful or loyal, often to a person or principle, but lacks the strong nuance of personal sacrifice found in 献身的.
Compound of 献身 (けんしん, 'devotion, self-sacrifice') and the adjectival suffix 的 (てき, '-like, -ish'). The base 献身 is itself from 献 (けん, 'offer, dedicate') and 身 (しん, 'body, self').