noun

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