Definition of "infinity"

infinity

/ɪnˈfɪnɪti/

noun
countable and uncountable, plural infinities
1. (uncountable) endlessness, unlimitedness, absence of a beginning, end or limits to size.
2. (countable, mathematics) A number that has an infinite numerical value that cannot be counted.
  Quotations
  Some of the most beautiful and thus appealing physical theories, including quantum electrodynamics and quantum gravity, have been dogged for decades by infinities that erupt when theorists try to prod their calculations into new domains. Getting rid of these nagging infinities has probably occupied far more effort than was spent in originating the theories.
  2012 January, Michael Riordan, “Tackling Infinity”, in American Scientist‎, volume 100, number 1, archived from the original on 30 April 2013, page 86
3. (countable, topology, mathematical analysis) An idealised point which is said to be approached by sequences of values whose magnitudes increase without bound.
4. (uncountable) A number which is very large compared to some characteristic number. For example, in optics, an object which is much further away than the focal length of a lens is said to be "at infinity", as the distance of the image from the lens varies very little as the distance increases further.
5. (countable, uncountable) The symbol ∞.