hypha(n = noun.plant) - any of the threadlike filaments forming the mycelium of a fungus;
is a kind of fibril, filament, strand
is a part of mycelium
has particulars: conidiophore, rhizomorph

   any of the threadlike filaments forming the mycelium of a fungus. See hyphae. [WordNet 1.5]

hypha, n. (pl. hyphae) a filament in the mycelium of a fungus.

Derivative:
hyphal adj.

Etymology:
mod.L f. Gk huphe web