Hisashi (廂), Omoya (母屋), & Mokoshi (裳階) are parts of a building.

— Hisashi (white)

Hisashi has two meanings, but in the context of the core sections of a building, it refers to a hallway like area around the omoya. It can surround it on all sides, three, two, or just one.

Corridors and unenclosed engawa under the extended eaves of the roof can also be refered to as hisashi.

In the irimoya roof style, the hipped part usually covers the hisashi.

The main purpose of hisashi is to strengthen a building, especially against side motion.

— Omoya (yellow)

The central part of a building. Before the introduction of Buddhism, omoya referred to the core of a residental building. After, moya referred to the core of a building directly under the main part roof. This area is considered sacred and contains an altar and other religous objects and images. The omoya is typically surrounded by the hisashi.

The floor level of the moya and the hisashi are the same throughout the entire building.

In the irimoya roof style, the gabled part usually covers the moya.

— Mokoshi (red)

Mokoshi (or shoukai) is a decorative pent roof surrounding a building below its true roof. They are typically seen in Buddhist temples and pagodas, especially those of Zen architecture in the late 12th century. It is used to hide the weight bearing pillars within the building.

It can either extend from the hisashi when present, or when it does not exist, from the omoya. It is a ken deep.

The mokoshi do not correspond to any internal structure of the building, which can lead to the thought that there are more floors in a building that there truely are.