背筋（せすじ、sesuji）
- back muscle

The Japanese word 背筋 背筋 refers to the muscles along your back, particularly those running from the base of your neck down to your lower back. It can also describe the back itself, or more figuratively, a person's posture and strength of character. It conveys a sense of strength, posture, and sometimes even determination.

⚫︎背筋を伸ばして座りなさい。 Translation: Sit up straight. ⚫︎彼女はいつも背筋が伸びている。 Translation: She always stands tall. ⚫︎運動をして、背筋を鍛える。 Translation: Do exercise and strengthen your back muscles.

This word is commonly used in everyday conversations to describe someone's posture or to refer to back muscles in the context of health or exercise. You can use it when someone is standing up straight, or when you are talking about strengthening your back through exercise. When describing posture, it can also imply confidence or strength of character.

⚫︎The word 背筋 背筋 is primarily written using the kanji 背 (se - back) and 筋 (suji - muscle, line, fiber). ⚫︎The reading is せすじ in hiragana. ⚫︎There is only one common way to write this word, and the okurigana is standard.

⚫︎背中 (senaka): back (anatomical term) ⚫︎腰 (koshi): lower back ⚫︎脊椎 (sekitsui): spine

⚫︎There is no direct antonym, but you could consider related concepts: ⚫︎猫背 (nekose): hunchback, stooped posture. (This describes the opposite of good posture)

彼は背筋をピンと伸ばして立っていた。 ・Translation: He was standing with his back straight. ・Explanation: This sentence describes someone's posture, emphasizing the straightness of their back.

毎日背筋を鍛えることで、姿勢が良くなった。 ・Translation: My posture improved by strengthening my back muscles every day. ・Explanation: This sentence explains how regular back muscle exercises led to improved posture.

The word 背筋 背筋 is a compound word. 背 (se) means "back," and 筋 (suji) means "muscle" or "line." Thus, 背筋 literally translates to "back muscles" or "line of the back."