myriad (plural myriads)

  1. (now historical) Ten thousand; 10,000 [from 16th c.]
  2. A countless number or multitude (of specified things) [from 16th c.]
    Earth hosts a myriad of animals.
    • Xenophon, Cyropaedia, Book I:
      How far he surpassed them all may be felt if we remember that no Scythian, although the Scythians are reckoned by their myriads, has ever succeeded in dominating a foreign nation …

Usage notes

Used as an adjective (see below), ‘myriad’ requires neither an article before it nor a preposition after. Because of this, some consider the usage described in sense 2 above, where ‘myriad’ acts as part of a nominal (or noun) group (that is, “a myriad of animals”), to be tautological.