The kanji character 筒 (筒) generally refers to something that is tube-shaped or cylindrical. It can describe a hollow, often elongated object. It suggests a container or passage, emphasizing its structure and form.

・On-yomi (音読み): トウ (tou) ・Kun-yomi (訓読み): つつ (tsutsu)

⚫︎望遠鏡の筒 Translation: Telescope tube ⚫︎水筒 Translation: Canteen; water bottle (literally: water 筒) ⚫︎封筒 Translation: Envelope (literally: seal 筒)