unfaithful

UK: ʌnˈfeɪθf(ə)l | US: ʌnˈfeɪθf(ə)l

Definition

  1. adj. not loyal or true to a partner, promise, or duty

  2. adj. inaccurate or unreliable (e.g., a description or translation)

Structure
un <not>faith <trust, loyalty>ful <adjective suffix>
Etymology

The word "unfaithful" combines three morphemes:

  1. "un-" (Old English "un-"), a prefix meaning "not," negates the root.
  2. "faith" (Old French "feid," Latin "fides"), meaning "trust" or "loyalty."
  3. "-ful" (Old English "-ful"), a suffix turning nouns into adjectives, implying "full of" or "characterized by."
    Originally tied to religious devotion ("faith"), the term evolved to describe betrayal in relationships or commitments. The logic is straightforward: "not full of loyalty."
Examples

  1. She felt heartbroken after discovering her partner was unfaithful.

  2. The unfaithful translation distorted the original poem’s meaning.

  3. His unfaithful behavior ruined their business partnership.

  4. The knight was branded unfaithful for abandoning his oath.

  5. An unfaithful account of events misled the investigators.