Nouns

(n)myriada large indefinite number“he faced a myriad of details”
(n)ten thousand, 10000, myriadthe cardinal number that is the product of ten and one thousand

Adjectives

(s)countless, infinite, innumerable, innumerous, multitudinous, myriad, numberless, uncounted, unnumberable, unnumbered, unnumerabletoo numerous to be counted“countless hours”, “an infinite number of reasons”, “innumerable difficulties”, “the multitudinous seas”, “myriad stars”