ENGLISH
REFERENCE

cos

conj. · n.
US //ˈkɔs// cos
  1. 1 because (conj.)
    B1 Intermediate Informal British English

    a short way to write or say 'because' in casual conversation.

    an informal clipping of 'because', used primarily in spoken English or casual digital communication.

    Example

    I didn't go to the party cos I was feeling really tired.

    Example

    He decided to skip the lecture 'cos he'd already covered the material during his summer internship.

    Usage

    Often written with an apostrophe as 'cos to show letters are missing.
    Pitfall
    I stayed home cos of the rain.
    I stayed home 'cause of the rain.

    While 'cos' is common in British texting, it is too informal for essays or professional emails; use 'because' instead.

  2. 2 lettuce (n.)
    B2 Upper Intermediate British English Cooking

    a type of lettuce with long, crisp leaves, often used in Caesar salads.

    a variety of lettuce (Lactuca sativa var. longifolia) characterized by long, narrow, crisp leaves and a firm rib.

    Example

    We need to buy some cos lettuce for the salad tonight.

    Example

    The chef prefers using cos for its superior crunch and ability to hold heavy dressings without wilting.

    Usage

    Commonly referred to as 'romaine' in American English.
    • romaine

Last updated June 19, 2026