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1

1 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of unit length is a line segment of length 1. In conventions of sign where zero is considered neither positive nor negative, 1 is the first and smallest positive integer. It is also sometimes considered the first of the infinite sequence of natural numbers, followed by 2, although by other definitions 1 is the second natural number, following 0. The fundamental mathematical property of 1 is to be a multiplicative identity, meaning that any number multiplied by 1 equals the same number. Most if not all properties of 1 can be deduced from this. In advanced mathematics, a multiplicative identity is often denoted 1, even if it is not a number. 1 is by convention not considered a prime number; this was not universally accepted until the mid-20th century. Additionally, 1 is the smallest possible difference between two distinct natural numbers. The unique mathematical properties of the number have led to its unique uses in other fields, ranging from science to sports. It commonly denotes the first, leading, or top thing in a group. One is most commonly a determiner used with singular countable nouns, as in one day at a time. One is also a pronoun used to refer to an unspecified person or to people in general as in one should take care of oneself. Finally, one is a noun when it refers to the number one as in one plus one is two and when it is used as a pro form, as in the green one is nice or those ones look good. One comes from the English word an, which comes from the Proto-Germanic root . The Proto-Germanic root comes from the Proto-Indo-European root *oi-no-. Compare the Proto-Germanic root to Old Frisian an, Gothic ains, Danish en, Dutch een, German eins and Old Norse einn. Compare the Proto-Indo-European root *oi-no- (which means "one, single") to Greek oinos (which means "ace" on dice), Latin unus (one), Old Persian , Old Church Slavonic -inu and ino-, Lithuanian vienas, Old Irish oin and Breton un (one).

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5 (five) is a number, numeral and digit. It is the natural number, and cardinal number, following 4 and preceding 6, and is a prime number. It has garnered attention throughout history in part because distal extremities in humans typically contain five digits. The evolution of the modern Western digit for the numeral 5 cannot be traced back to the Indian system, as for the digits 1 to 4. The Kushana and Gupta empires in what is now India had among themselves several forms that bear no resemblance to the modern digit.
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2 (two) is a number, numeral and digit. It is the natural number following 1 and preceding 3. It is the smallest and only even prime number. Because it forms the basis of a duality, it has religious and spiritual significance in many cultures. The digit used in the modern Western world to represent the number 2 traces its roots back to the Indic Brahmic script, where "2" was written as two horizontal lines. The modern Chinese and Japanese languages (and Korean Hanja) still use this method.
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