your hair=あなたの[髪](https://eikaiwa.dmm.com/uknow/questions/63055/)の毛 です
Grown（=[伸びた](https://eikaiwa.dmm.com/uknow/questions/58856/)）はgrowの過去形なのでこの場合はこれを使います
heaps＝たくさん
質問にお答えする感じだと
to tell someone that you haven't seen in a long time that their hair has grown you can say, "Wow!! your hair has grown heaps"
「久しぶりに会った友人に髪が伸びたことを伝える時は"Wow!! your hair has grown heaps"と言えます。
The word "wow" is used to show the excitement in your voice and that you are happy.
We use "longer" to compare two items and longest for more than two items. In this case you are comparing two time periods.
Yes, people may change considerably if you don't see them for an extended period of time. They may put on weight, age, get pregnant - or change their hair.
"Hey Sue, where have you been the last five years?"
"I married an American. We have two kids."
"That's great to hear. Wow your hair has grown since last time we met!"
"Yes, I always keep it long these days."
"Well, it suits you!"
We also describe hair as luxuriant, thick, and healthy.
Also the word flowing means the hair is hanging in an attractive way.
For example, "Your hair long is long and flowing".
髪の毛に使える形容詞は、 luxuriant, thick, healthyなどがあります。
また、 flowing は、髪の毛が魅力的にたなびくという意味です。
例
"Your hair long is long and flowing".
君の髪が長くたなびいている。
Both of these sentences are a great way to let someone know that their hair has grown since you last saw them. You can also ask if they like it that length, if they would like to cut it, or what they did to make their hair grow so fast.
examples
"wow, your hair has grown so much since i last saw you".
or
"wow, your hair grew long !".
or
"i cannot believe how long your hair is".
例文
"Wow, your hair has grown so much since I last saw you".
わぁ、前回会ってから髪の毛が本当に伸びたね
"Wow, your hair grew long !".
わぁ、髪の毛が伸びたね
"I cannot believe how long your hair is".
髪の毛がそんなに長いなんて信じられない
Commenting on someone’s hair is a nice way to break the ice and pay a compliment at the same time. Your hair has grown or gotten longer both imply a change from the last time you met. Whereas are you growing your hair would show a change in length but also allow the person you are talking to a chance to respond and talk
場を和ませたり、相手を褒めたいときは、髪について話すといいですね。
「Your hair has grown」「Your hair has gotten longer」どちらも、その前に会ったときから変化していることを表します。
「Are you growing your hair?」も髪の毛が伸びたことを表しますが、こちらは質問です（相手の返答を待ちます）。
We can use the verb, "to grow," to refer to the change in length, height, age, etc. or something. We can also use the more general verb, "to change," to refer that something was different that how we're used to seeing it before. Lastly we can use the phrase, "has gotten longer," in the case that the hair was longer than the last time we saw it.
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