外壁（がいへき、gaiheki）
- outer wall

The Japanese word 外壁, read as がいへき (gaiheki), directly translates to "exterior wall" or "outside wall." It refers to the outer structural walls of a building. These are the walls that form the external surface and provide protection from the elements such as weather, wind, and sunlight. 外壁 is a crucial part of a building's structure and contributes significantly to its appearance and durability. The term encompasses the materials used for the construction of these walls.

⚫︎その家の外壁は木でできています。 Translation: The exterior walls of that house are made of wood. ⚫︎外壁の塗装が剥がれてきたので、塗り替えが必要です。 Translation: The paint on the exterior walls is peeling, so it needs to be repainted. ⚫︎新しいマンションの外壁はタイル張りです。 Translation: The exterior walls of the new apartment building are tiled.

You would use 外壁 when talking about the outer walls of a building, such as discussing construction, maintenance, or the materials used. It's used in conversations about home improvement, architecture, and real estate. It's a common term in discussions related to building structures and designs.

外壁 is primarily written using kanji and hiragana. ・Kanji: 外壁 ・Hiragana reading: がいへき There are no other common ways to write this word. The okurigana is fixed.

While there isn't a direct synonym that is widely used, one could use more descriptive phrases depending on the context. Some options that focus on the material include: ・壁（かべ - wall） - Can be used more broadly. ・外装（がいそう - exterior) - While not identical, it can sometimes be used in a similar context.

There aren't specific antonyms in the direct sense. The opposite would be "interior walls," but there's no single Japanese word specifically meaning "not exterior wall". You could use something like: ・内壁（ないへき - interior wall）

この建物の外壁は地震に強い構造になっています。 ・Translation: The exterior walls of this building have a structure that is resistant to earthquakes. ・Explanation: This sentence discusses the structural properties of the exterior walls, specifically their earthquake resistance.

外壁のひび割れを放置すると、雨漏りの原因になります。 ・Translation: If you leave cracks in the exterior walls unattended, it can cause water leaks. ・Explanation: This sentence explains the consequences of neglecting the maintenance of the exterior walls.

The word 外壁 is formed by combining the kanji 外 (gai), meaning "outside" or "exterior," and 壁 (heki), meaning "wall." Thus, the word directly reflects the meaning of "exterior wall."