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headache

n.
US //ˈhɛˌdeɪk// UK //hˈɛdeɪk// headache
  1. 1 physical pain (n.)
    A2 Elementary Medicine

    a pain or ache inside your head.

    a continuous pain in the head, ranging from mild discomfort to severe migraine.

    Example

    I need to lie down because I have a terrible headache from the loud music.

    Example

    The patient reported a persistent, throbbing headache that worsened whenever he was exposed to bright fluorescent lighting.

    Pitfall
    I have a head ache.
    I have a headache.

    Headache is written as one single word, not two separate words.

  2. 2 a problem (n.)
    B2 Upper Intermediate Informal

    something that causes you a lot of worry or trouble.

    a person or situation that causes significant annoyance, worry, or difficulty. Often used in professional or logistical contexts.

    Example

    Organising the office party was a real headache because everyone wanted different food.

    Example

    The sudden change in tax regulations has created a major administrative headache for small business owners across the country.

Origin

From Middle English hevedeche, from Old English hēafodeċe, equivalent to head + ache.

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