Individually = One alone, one on its own.
Separately = Apart from the others, alone.
'One by one' distinguishes 'one' from a 'group as a whole'.
"The children went into the classroom one by one as the teacher read out their names.'
Individually = 自分一人で、自分自身で
Separately = 他とは離れて、ひとりで、.
'One by one' （１つずつ）は'one' from a 'group as a whole' （グループの中から１つ）.という意味とは異なります。
"The children went into the classroom one by one as the teacher read out their names.'
例：子供たちは先生に呼ばれて一人ずつ教室にはいっていった。
"Separate"- "Individually" - "Singly" it all means that you don't want your items together.
"Can you pack each item, separately, please?"
"Please wrap them individually."
"Please wrap them singly."
Separate, individually, Singlyとは、全て一緒にして欲しくないときに使う表現です。
例
"Can you pack each item, separately, please?"
それぞれべつに包んでもらえますか？
"Please wrap them individually."
個別で包んでもらえますか？
"Please wrap them singly."
ひとつひとつ包んでもらえますか？
Would you be able to wrap each one individually, please?
The first part of the sentence involves polite and formal speech.
"Could you...?" and "Would you be able to...?" Could be substituted with other words, too, but these are my suggestions.
"to wrap" is our verb. It means to cover something with Something else (for example, gift wrap, paper, material, etc.)
Next, you could say "item" to refer to the noun (object) that you want to be wrapped. You could also use the word "one" as the staff member will understand that you are referring to the item in front of you.
Saying "each one, individually" and "separately" allows the staff member to know that they should only do one item at a time and not everything at once.
最初の文は、丁寧でフォーマルな言い方です。
"Could you...?" （～して頂けますか）や、 "Would you be able to...?" （～して頂くことは可能ですか）は、他の単語で言い換えることもできますが、こちらは私のおすすめの表現です。
"wrap"は動詞です。"wrap"は、何か（例えばギフト用の素材、紙、その他の素材等）で、品を包むという意味です。
続いて、"item"（品）は、包んでもらいたい名詞（品）を指します。目の前にある品で店員さんは何の話をしているかわかるので、"one"という単語を使うこともできます。
"each one, individually"（個別に）や、"separately"（別々に）と言うと、店員さんに品を一つずつ包んでもらって、全て一緒に包んでもらうのではないというのが伝わります。
▪ Wrap each item on its own.
▪ Wrap it separately.
▪ Each item to be wrapped alone.
All the above phrases indicate that each item must be wrapped in its own packaging and must be done individually.
Example sentences
a. Can you please wrap each item on its own.
b. I would like you to wrap it separately.
c. Is it possible for each item to be wrapped alone.
▪ Wrap each item on its own.
▪ Wrap it separately.
▪ Each item to be wrapped alone.
（それぞれの商品を包んでください。）
上記のフレーズは、商品をそれぞれのパッケージごとに、別々に包んでもらわなければならないということを示しています。
例文
a. Can you please wrap each item on its own.
（それぞれの商品を包んでもらえますか。）
b. I would like you to wrap it separately.
（商品を別々に包んでもらいたいです。）
c. Is it possible for each item to be wrapped alone.
（それぞれの商品ごとに包んでもらうことは可能ですか。）
When buying several things at a store, and you would like to ask the staff to wrap each item separately, you can say:
"Could you please wrap these separately?"
"Can you wrap these individually?"
お店で複数の物を買ったとき、それぞれの商品を包装してもらいたいなら、次のように言えます。
"Could you please wrap these separately?"（これらを別々に包装してもらえますか）
"Can you wrap these individually?"（これらを一つ一つ包装してもらえますか）
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