Myriad is a classical Greek name for the number 10⁴ = 10 000, or a group of 10 000 people, etc. In English, the word refers to 10 000 (a cardinal number) or to an unspecified large quantity.

The term myriad is a progression in the commonly used system of describing numbers using tens and hundreds. For example, one names small numbers in terms of number of tens plus the remainder, e.g., 76 is seventy six or seven tens plus six. This system works until ten tens, which requires a new description, a hundred. One similarly names numbers less than 10,000 by counting the number of hundreds plus the rest, e.g., 1776 is seventeen hundred and seventy six. This system works until one hundred hundred, which again requires a new name, a myriad. Similarly, the system using myriads works up to a myriad myriad, or one hundred million, which was left as the largest named number by the Ancient Greeks and is also the largest named number in the Bible.

A myriad is primarily a singular cardinal number; just as the 'thousand' in 'four thousand' is singular (one does not write 'four thousands people') the word myriad is used in the same way: "there are four myriad people outside". When used as a noun, meaning 'a large number', it follows the same rules as that phrase.

In English, the term "myriad" is most commonly used to refer to a large number of an unspecified size. In this way "myriad" should be used as an adjective. Thus "there are myriad people outside" is correct and "There are a myriad of people outside" is not.

There are also words in other languages with the same classic meaning as "myriad":

• Hebrew: revava
• Chinese: wan4 Mandarin and maan6 Cantonese (萬/万)
• Japanese:man (万/萬)
• Korean: man (万/만/萬)

Chinese, Japanese and Korean also have words for a myriad squared (100,000,000): yi4(億), oku (億), and eok (억/億)(pronounced "awk"), respectively. A myriad cubed (10 000³) is a zhao4 (兆); cho (兆); a myriad to the fourth power (10 000⁴) is a jing1 (京); kei (京). Conversely, Chinese, Japanese and Korean do not have single words for a thousand squared, cubed, etc., unlike English.

The English numbering system divides large numbers into groups of three digits, and so the names for such numbers follow this division (10 000 = ten thousand). East Asian numbering divides large numbers into groups of four; so in Chinese, Japanese, or Korean, 30 000 really would be "three myriad" (3 0000 - Japanese san-man). One million is a hundred myriad (100 x 10000 instead of 1000 x 1000); the next uniquely named number after a myriad is 億, which is myriad myriad (10000 x 10000) or a hundred million.

Modern Greek still uses the word "myriad" by itself, but also to form the word for million. The word for million is ekatommyrio (hundred myriad - εκατομμύριο); one thousand million is disekatommyrio (twice hundred myriad - δισεκατομμύριο).

The largest number named in Ancient Greek was a myriad myriad and Archimedes of Syracuse used this quantity as the basis for a numeration system of large powers of ten, which he needed to count grains of sand, see The Sand Reckoner.

There is only slight indication that "myria" has at all been used as a metric prefix for 10,000, e.g., 10 kilometres = 1 myriametre. It does not have official status as an SI prefix.

In Sweden, one mile = 10 000 meters = one myriameter. Before Sweden went metric, one Swedish mile was 10 688 meters, so only a small change had to be made to the old Swedish mile to make it equal to one myriameter. Even today, Swedes frequently use the Swedish mile to refer to travel distances in everyday language.

See also

• Chinese numerals
• Indian numbering system

Integers | Large numbers

Myriade | Miríada | 10000 | Myriade