If a person is the youngest in a group, you can simply state that this individual is "the youngest". This means that everyone else within the group is older. A commonly used phrase is to say, "The baby of the group. This phrase illustrates someone is the youngest as it refers to them as a "baby".
グループの中で最も若い人のことはシンプルに"the youngest"（一番若い）と表せます。これは、他の人がその人よりもみんな年上であることを表します。
よく使われるフレーズに"the baby of the group"というのがあります。これも最も若い人を表します。最も若い人を"baby"（赤ちゃん）と表しています。
Sometimes among friends it may be funny to tease the youngest person by calling them the:
'Baby of the group'
That means they are the youngest. This would be an informal phrase to tease a close friend.
Otherwise it is suitable to just say:
The youngest.
I hope that helps!
友人同士では、最年少の人を冗談でこう呼ぶこともあるかもしれません。
Baby of the group
こう言うと、その人は最年少という意味になります。これは、仲の良い友人をからかったりするカジュアルな言い方です。
もしくはこう言うことも適切でしょう。
The youngest（一番若い）
参考になればうれしいです！
a person who is the least old of a group
'He is the youngest in the group.'
'I am the youngest in my family.'
'I am two years older than my youngest sibling.'
あるグループで最年少の人です。
He is the youngest in the group.
彼はそのグループで最年少です。
I am the youngest in my family.
私は、家族で一番したです。
I am two years older than my youngest sibling.
私は、一番下の兄弟より２歳年上です。
The person who is the youngest in a group is called the youngest.
If you have a group and someone was the last to join that group, you can call them the newcomer.
Tender age = a time in your life when you are still young and lack experience.
"Tennis players start at a more tender age these days."
At the tender age of something:
"He was first elected at the tender age of 23."
"They were a party of 17 rugby players with an age range of between 17 and 29.
The youngster of the party was Rupert, age 17."
Juvenile = childish; immature, infantile, babyish
"She's bored with my juvenile conversation."
Tender age = 若くてまた未成熟な人生の期間を言います。
"Tennis players start at a more tender age these days."
最近のテニスプレーヤは若いうちからテニスを始めているんだよね。
At the tender age of something（弱冠）
"He was first elected at the tender age of 23."
例
"They were a party of 17 rugby players with an age range of between 17 and 29. The youngster of the party was Rupert, age 17."
17歳から29歳までの17人のラグビー選手のパーティがあった。そのパーティの若者の一人、ルパートは17歳だ。
Juvenile = 子供っぽい、幼稚な、未成熟な、お子様な、など
例
"She's bored with my juvenile conversation."
彼女は幼稚な会話にうんざりしていた。
When talking about the ages of people or your children then we always refer to the youngest age person as simply 'the youngest' as they are younger in age
You can also use the term 'the baby of the group' meaning the youngest in age in the group
自分の子どもなどについて、最も年齢が若いことを表すときには、'the youngest'（最も若い）を使います。
他に、'the baby of the group'という表現も使えます。グループの中で最も年齢が若い人を表します。
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