myriad

Myriad is a noun that means a countless or extremely great number. In modern English it is also used as an adjective before a noun to indicate many or countless, as in "a myriad of options" or "myriad challenges."

Etymology: The word comes from Greek μυριάς (myrias), meaning ten thousand. It entered English in the late 16th century, originally referring to that exact number, and over time broadened to denote a vast but indefinite quantity.

Usage and forms: As a noun, myriad historically appears in the plural form "myriads," though the singular "a myriad" is common in contemporary prose when paired with "of" (a myriad of options) or used attributively (myriad possibilities). As an adjective, myriad precedes a noun (e.g., myriad stars) and is sometimes used with or without "of" (a myriad of stars).

Synonyms and tone: Synonyms include multitude, countless, innumerable, and abundance. The term is common in literature, journalism, and academic writing but is considered somewhat formal or literary in everyday speech.