myriad

In English, the "ten thousand" sense of myriad mostly appears in references to Ancient Greece, such as the following from English historian Connop Thirwall's History of Greece: "4000 men from Peloponnesus had fought at Thermopylae with 300 myriads." More often, English speakers use myriad in the broad sense—both as a singular noun ("a myriad of tiny particles") and a plural noun ("myriads of tiny particles"). Myriad can also serve as an adjective meaning "innumerable" ("myriad particles"). While some usage commentators criticize the noun use, it's been firmly established in English since the 16th century, and in fact is about 200 years older than the adjective. Myriad comes from Greek myrias, which in turn comes from myrioi, meaning "countless" or "ten thousand."