Height
Back, Spine
noun
The kanji and the word are exactly the same. That means they share meanings as well.
Since this word is made up of a single kanji, it probably uses the kun'yomi reading. You did not learn this reading, so here's a mnemonic to help you:
Where you're from, everyone measures their height in celery (せ). No inches or centimeters for you, it's celery sticks only. How many celery sticks tall are you?
しばらく見ない間に背、のびたね！
You've grown taller in the time we haven't seen each other!
背の順に並んでください。
Please line up in order of height.
彼はカベに背をもたれかけながら、本を読んでいました。
He was reading a book while resting his back against the wall.
紫色のドレスを着ている背の高い女性は、あなたのご友人ですか？
Is your friend the tall woman in the purple dress?