English Reference
adjective

conscientious

adj.
US /ˌkɑnʃiˈɛnʃəs/ UK /kˌɒnsɪˈɛnʃəs/ con·sci·en·tious

  1. 01 C1 Advanced AcademicFormal

    working hard and being very careful to do your job or task correctly.

    characterised by extreme care, thoroughness, and effort in performing tasks.

    Simple

    A conscientious student always checks their work for mistakes before handing it in.

    In context

    The researcher was exceptionally conscientious, documenting every minor variable to ensure the experiment could be replicated by others.

    Usage

    Typically used to describe workers, students, or the quality of the work itself.

  2. 02 C1 Advanced Formal

    doing what you believe is right and honest, even when it is difficult.

    governed by or conforming to the dictates of conscience; principled.

    Simple

    He was a conscientious person who refused to lie, even to protect himself.

    In context

    The judge was known for her conscientious approach to the law, always weighing the moral implications of her rulings.

    Teacher's tip

    Often appears in the phrase 'conscientious objector', referring to someone who refuses to join the military for moral reasons.

    principledscrupulousupright
    unprincipledimmoral

I am lucky to be with a very good agency , which only employs highly competent and conscientious staff (from all over the world).

The Guardian· 30 Aug 2026

She added that conscientious objection in Wales – where staff can refuse to take part in care on moral or religious grounds – was "widespread" and making a "bad situation" with provision worse.

BBC News· 17 Aug 2026

From Middle French conscientieux, from Medieval Latin cōnscientiōsus. Its English equivalent could possibly be analyzed as conscient + -ous. See more at conscience.

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

This entry
Origin la-med cōnscientiōsus
Level C1 · Advanced
Frequency Frequent
Updated