Youthful = when someone ilooks youthful, they have the appearance or physical attributes of someone younger.
"Jane looks so youthful. Is she really 50 years old?"
"Yes, I think it's because she works out every day"
Youthful = youthfulと表現するとき、相手のルックスや身体が若く見える、感じるときに使います。
"Jane looks so youthful. Is she really 50 years old?"ジェーンは本当に若いよね、本当に50歳なの？
"Yes, I think it's because she works out every day" ああ、彼女はいつも鍛えているからね。
"You look young for your age" means that you look younger that what you really are.
You can also say "spring chicken" it means a young person.
A : How old are you?
B : I am 50 years old.
A : You look young for your age!
B : I am no spring chicken!
You look young for your age" 実年齢よりよっぽど若く見える、という時に使います。
"spring chicken" .と若い人に対して使うこともできます。
A : How old are you? おいくつですか？
B : I am 50 years old. 50歳になります。
A : You look young for your age! お若いですね。
B : I am no spring chicken! もう若者ではないさ。
Although she was 55 ...she was still fresh-faced... with a youthful apearance!
When someon looks "younger than their years" ,,,we might describe them as being fresh-faced and youthful looking;-D
"Although she was 55 ...she was still fresh-faced...with a youthful apearance!"
人が年齢よりも若く見えるとき...「fresh-faced and youthful looking」と表せます。
"Although she was 55 ...she was still fresh-faced...with a youthful apearance!"（彼女は55歳だったけど...若く見えた）
Young (adjective)
having lived or existed for only a short time
Example:
A: How old are you?
B: 27 years old
A: You look young
_______________________________________________
Youthful (adjective)
this means young or seemingly young
A: You look youthful
B: Thank you! I have been working out and eating healthy food
_________________________________________________
Young-looking (adjective)
means to have a youthful appearance
Young(形容詞) 短い間のみ存在している、生きている/生きていた
例
A: How old are you? いくつですか？
B: 27 years old 27歳です。
A: You look young お若くみえますね。
________________________
Youthful: youngまたは若く見える、という意味で使われます。
A: You look youthful: 若く見えますね。
B: Thank you! I have been working out and eating healthy food: ありがとう。筋トレと健康にいいご飯をいつも食べているんです。
_________________________________________________
Young-looking 形容詞 容姿が若い時に使います。
おっしゃられている内容は、
You look young.
「あなたは若く見える」
のように表現できます。
もう少し説明的に言うなら、
You look younger than you are.
「あなたは実際よりも若く見える」
のように言っても良いですね。
以上です。
少しでも参考になれば幸いです(*^_^*)
アメリカ合衆国 
日本 
南アフリカ 
イギリス 
