English Reference
adjective · noun

faithful

adj. · n.
US /ˈfeɪθfəɫ/ UK /fˈeɪθfəl/ faith·ful UK spelling faithfuls

  1. 01 B2 Upper Intermediate

    adj.staying loyal to a person, a group, or a set of beliefs over a long time.

    adj.adhering firmly and devotedly to a person, cause, or idea.

    Simple

    He remained a faithful friend even during the most difficult years of her life.

    In context

    Despite the political upheaval, the general remained faithful to the constitution, refusing to support the attempted coup.

  2. 02 B2 Upper Intermediate

    adj.having a sexual relationship with only one person, such as a husband or wife.

    adj.remaining sexually loyal to a single spouse or long-term partner.

    Simple

    They promised to be faithful to each other when they got married.

    In context

    The study examined the social factors that encourage couples to remain faithful throughout decades of marriage.

    unfaithfuladulterous
  3. 03 C1 Advanced Formal

    adj.exactly like the original thing or the truth.

    adj.representing something with a high degree of accuracy or truth; consistent with reality.

    Simple

    The film is a faithful version of the famous book.

    In context

    The architect insisted on a faithful restoration of the cathedral, using only materials that were available in the twelfth century.

    inaccuratefalse
  4. 04 C2 Proficiency Technical Math

    adj.a technical way to describe certain types of mathematical relationships.

    adj.describing a representation or functor that is injective, or a module whose annihilator is zero.

    Simple

    The professor explained why this specific representation is considered faithful.

    In context

    In category theory, a faithful functor is one that is injective on morphisms for every pair of objects in the source category.

    injective
  5. 05 C1 Advanced Formal Religion

    n.the people who follow a religion or a specific cause.

    n.the collective body of practicing members of a religion or devoted followers of a movement.

    Simple

    The priest spoke to the faithful during the morning service.

    In context

    The party leader gathered the faithful for a final rally on the eve of the national election.

    Usage

    Usually used as 'the faithful' to refer to a group of people.

McCormack said the Nostell version is “understood to be the most faithful to Holbein’s original and the only same-size version that survives”.

The Guardian· 3 Sept 2026

Did they mean that she should be more faithful to the original poem?

Smithsonian Magazine· 17 Jul 2026

From Middle English feithful, equivalent to faith + -ful.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Middle English feithful
Level B2 · Upper Intermediate
Frequency Common
Updated