Definition of O in English:


(also o)


  • 1The fifteenth letter of the alphabet.

    • ‘Little do you know, I used to be obsessed with a capital O.’
    • ‘Note the graceful shape of the o and s, and the fullness of the counters.’
    • ‘For capital O, always form a C first, and then close it up.’
    1. 1.1 Denoting the next after N in a set of items, categories, etc.
      • ‘Susan Brown covers M, N, and O in her series that helps you to change your life at your own pace.’
    2. 1.2 A human blood type (in the ABO system) lacking both the A and B antigens. In blood transfusion, a person with blood of this group is a potential universal donor.
      • ‘There are three alleles or versions of the blood type gene: A, B, and O.’
      • ‘The leading factor in weight gain for Type Os is the gluten found in wheat germ and whole wheat products, which interferes with insulin efficiency and slow down metabolic rate.’
      • ‘Type Os don't find dairy products and grains quite as user friendly as do most of the other blood types.’
  • 2Nought or zero (in a sequence of numerals, especially when spoken)

    ‘two seven o seven point six’
  • 3A shape like that of a capital O; a circle.

    ‘he made an O with his mouth’
    • ‘Pacing is especially troublesome - round shapes like "O" need less white space on either side than straight shapes like "H," of course, but there's also the question of how much white space the whole font needs.’
    • ‘Is there no way to rotate/ flip individual objects independently? e.g., when the O shape is brought into 3D it is in a vertical position.’