myr·i·ad 
(mĭrē-əd)
(mĭrē-əd)adj.
1. Constituting a very large, indefinite number; innumerable: the myriad fish in the ocean.
2. Composed of numerous diverse elements or facets: the myriad life of the metropolis.
n.
1. A large, indefinite number: a myriad of microorganisms in the pond; myriads of stars in the galaxy.
2. Archaic Ten thousand.
[Greek mūrias, mūriad-, ten thousand, from mūrios, countless.]
Usage Note: Throughout most of its history in English myriad was used as a noun, as in a myriad of reasons. In the 1800s, it began to be used in poetry as an adjective, as in myriad dreams. Both usages in English are acceptable, as in Samuel Taylor Coleridge's "Myriad myriads of lives." This poetic, adjectival use became so well entrenched generally that many people came to consider it as the only correct use. In fact, however, both uses are acceptable today.