why not...? - definition and synonyms

phrase spoken
  1. 1
    used for making a suggestion

    Why don’t we share the cost of accommodation?

    why not do something:

    Why not stay for lunch?

  2. 2
    used for agreeing to a suggestion or request

    ‘Perhaps we could all meet up at your house?’ ‘Yes, of course, why not?’

See also main entry: why