1. This is an expression of pain :-(
2. This is another expression of pain :-(
3. When something is 'red hot' such as metal, it glows red. So something that is 'red hot' means something extremely hot and certainly, too hot to touch.
Ouch!
This is an exclamation
This expresses pain
Example
Ouch! I burn my hand with the coffee.
______________________________________________________
That's hot!
This will let people around you know that and object is hot and to be cautious
A: That's hot!
B: What?
A: The fries are really hot
Ouch!
これは感嘆符です
これは痛みを表します
例
Ouch! I burn my hand with the coffee.（熱っ！コーヒーで手をやけどした）
______________________________________________________
That's hot!
これは周りの人に何かが熱く注意が必要だということを知らせる表現です
A: That's hot!（それは熱いよ！）
B: What?（何？）
A: The fries are really hot（その揚げ物はとても熱いよ）
1=This sentence may be used when you may have touched a hot surface but not fully injuring yourself.
And there are times when you are around other people and would be the courtesy to let them know what you just touched is hot/very hot.
2=using the adjective form of 'snap' this will show when accidentally touched a hot surface without knowing and has caught you by surprise.
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