The Collaborative International Dictionary of English v.0.48:

hypha \hypha\, n.; pl. hyphae.
   any of the threadlike filaments forming the mycelium of a
   fungus. See hyphae.
   [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Hyphae \Hy"ph[ae]\, n. pl. [NL., fr. Gr. "yfh` a web.] (Bot.)
   The long, branching filaments of which the mycelium (and the
   greater part of the plant) of a fungus is formed. They are
   also found enveloping the gonidia of lichens, making up a
   large part of their structure.
   [1913 Webster]