Large number

The phrase "large number" has a subjective meaning, which is unsatisfactory for googologists because their studies rely on the definition of the term. Informally, it could be defined as "a number larger than any one used in everyday life." To a politician, this may be a trillion euros; to a cosmologist, 1026 meters.

Sbiis Saibian suggested defining a large number as any greater than 1, offering the alternate term superuniary number. Small numbers would be those smaller than 1. This definition has the advantage that it makes the small numbers the reciprocals of the large ones.

Until January 2013, Googology Wiki only considered numbers at least 100 to be large numbers, and thus suitable for inclusion.

Kyodaisuu in Japanese
In Japanese, kyodaisuu (巨大数) means a very large number. "Kyodai" (巨大) means very large, "kazu" (数) means number, where it changes to "suu" when combined as a single word as kyodaisuu. Therefore, kyodaisuu means not just a large number, but has a connotation that it is a super-huge number.

wrote that the first appearance of the word 巨大数 in his knowledge is an article in 日経サイエンス magazine, which is a translation of the article "The challenge of Large Numbers" in Scientific American by. According to Fish, the word 巨大数 spread in Japanese internet community in the thread of 巨大数探索スレッド (Thread for the search of kyodaisuu) in Japanese textboard, which started in 2002. In the thread, people were creating and analyzing large numbers which exceed Graham's number, such as Fish numbers, and for expressing such large numbers, people started to use the word kyodaisuu, to express unimaginably large numbers. Therefore, the word kyodaisuu has a connotation that it is an unimaginably large number.

In Japanese googology community, 6 is considered to be kyodaisuu with the Japanese phrase "6は巨大数" (6 is a kyodaisuu), partially as a sort of a joke. For a detail on the historical background, see Flan numbers.