aleph number
alef symbol (U+2135) or aleph, written left-to-right as the mathemical symbol ‹ℵ› for the first transfinite cardinal (countable); ordered sequence of transfinite numbers used to represent the cardinality (or size) of infinite countable sets
en-GB/ˈælɛf ˈnʌmbə/
en-US/ˈɑləf ˈnʌmbɚ/