Hypha (pl. Hyphae)
Hypha
Japanese: 菌糸（ハイファ）
Thread-like elongated cell structures extended by filamentous fungi such as molds and koji mold. They grow from the tip and spread through substrates while branching.
Hyphae are thread-like structures extended by molds and koji mold. They grow continuously from the tip, branching as they advance into substrates in search of nutrients.
In koji-making, when they say 'haze has entered,' it means hyphae have penetrated into the interior of rice grains. The deeper the hyphae reach, the more thoroughly enzymes break down the rice.
A mass of hyphae is called a mycelium. In fact, what we call a mushroom is merely a small part of a vast mycelium spreading beneath the ground.