English Reference
adjective · noun

accidental

adj. · n.
US /ˌæksəˈdɛnəɫ/ UK /ˌæksɪdˈɛntəl/ ac·ci·den·tal UK spelling accidentals

  1. 01 B1 Intermediate

    adj.happening by chance or by mistake, rather than being planned.

    adj.occurring by chance, unexpectedly, or without deliberate intent.

    Simple

    The police believe the fire was accidental and started in the kitchen.

    In context

    The discovery of the ancient coins was entirely accidental, occurring while the construction crew was digging a trench for new water pipes.

  2. 02 C1 Advanced Technical Music

    n.a symbol like a sharp or flat that changes a note for a short time.

    n.a sign placed before a note which alters its pitch by a semitone, independent of the key signature.

    Simple

    The pianist missed the accidental in the third bar and played a wrong note.

    In context

    The composer used frequent accidentals to create a sense of tonal instability throughout the second movement.

    Usage

    The noun refers to the symbol itself (the sharp, flat, or natural sign).

  3. 03 C2 Proficiency AcademicFormal Philosophy

    n.a quality or feature of something that is not necessary for it to be what it is.

    n.a property or attribute that is not part of the essential nature of a thing.

    Simple

    The color of the car is an accidental; it doesn't change the fact that it is a car.

    In context

    In Aristotelian logic, an accidental is a quality that can be changed without the subject losing its fundamental identity.

    contingencynon essential

Over that period, the laboratory received 274 samples connected to 201 suspected cases of either deliberate or accidental poisoning across the UK, Ireland, and Gibraltar.

ScienceDaily· 15 Aug 2026

The brief argues that the harms young people face online are not accidental.

UN News· 10 Aug 2026

From Middle English accidental, from Anglo-Norman accidentel, Middle French accidentel, accidental, and their source, Late Latin accidēntālis; corresponding to accident + -al.

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

This entry
Origin la-lat accidēntālis
Level C2 · Proficiency
Frequency Frequent
Updated