開通（かいつう、kaitsuu）
- opening to traffic

The Japanese word 開通 （かいつう, *kaitsuu*） primarily means "opening," "connection," "establishment," or "completion" of a pathway, route, or system, making it ready for use. It often implies that something previously blocked or unavailable is now accessible or functioning. The word conveys the idea of enabling passage or communication. It can refer to physical infrastructure like roads and railways, or more abstract systems like communication networks. The 開通 of something signifies its readiness and availability for its intended purpose.

⚫︎ 新幹線が 開通 しました。 Translation: The Shinkansen (bullet train) line opened. ⚫︎ インターネット回線が 開通 しました。 Translation: The internet connection was established. ⚫︎ 新しい道路が 開通 して、交通が便利になりました。 Translation: The new road opened, making transportation convenient.

This word is used in formal and informal contexts. It's common to hear it when discussing the opening of new infrastructure, such as train lines, roads, or communication networks. It can also describe the activation or establishment of services. You would use 開通 when you want to specifically indicate the moment something becomes operational. It's often used in news reports, announcements, and technical descriptions.

開通 is typically written in kanji. The reading is *kaitsuu*. The okurigana (*tsuu*) is consistent.

⚫︎ 開通する（かいつうする）- To open, to connect (verb form) ⚫︎ 開通式（かいつうしき）- Opening ceremony (for roads, etc.) ⚫︎ 開拓（かいたく）- Opening up, development (broader sense, also used for new lands) ⚫︎ 開始（かいし）- Start, commencement (more general term)

⚫︎ 閉鎖（へいさ）- Closure, shutdown ⚫︎ 通行止め（つうこうどめ）- Road closed ⚫︎ 不通（ふつう）- Disruption, interruption (of service)

高速道路の新しい区間が昨日 開通 しました。 ・Translation: The new section of the highway opened yesterday. ・Explanation: This sentence describes the completion and availability of a new section of highway.

電話回線が 開通 するまで、少し時間がかかりました。 ・Translation: It took a little while before the phone line was connected. ・Explanation: This sentence discusses the time it takes to activate a telephone service.

開通 is composed of two kanji: 開（かい, *kai*), meaning "open" or "begin," and 通（つう, *tsuu*), meaning "pass," "go through," or "communicate." Therefore, the etymology directly reflects its meaning of "opening" or "making passable," establishing a connection.