Definition of infinities:
(n) :
(uncountable) endlessness, unlimitedness, absence of a beginning, end or limits to size.
(n) :
(countable, mathematics) A number that has an infinite numerical value that cannot be counted.
(n) :
(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.
(n) :
(countable, uncountable) The symbol ∞.
(n) :
(countable, topology, mathematical analysis) An idealised point which is said to be approached by sequences of values whose magnitudes increase without bound.