The normal temperature of the human body is 36.5C.

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1. thirty two degrees point Celsius
2. thirty-two degrees point Celsius
(Which one is correct? When do we use the hyphen '-'?)

It should be

thirty-six point five degrees Celsius.

The hyphen is used in all two-word numbers from twenty-one through ninety-nine.

The hyphen is used correctly in "thirty-two". One would write out 126 as "one hundred twenty-six", etc.

One would not usually write out the temperature, though. And "thirty-two degrees point..." makes no sense. It's "32 degrees Celsius". The word "point" is only used to indicate a decimal. Point what?

If you begin a sentence with the number, you should write it out: "Thirty-six point five Celsius is the normal temperature of the human body." Inside the sentence, we use the numerals 36.5.

When writing a temperature, it is commonly written as "thirty-two degrees Celsius" without a hyphen. The hyphen is not necessary in this context. However, if you are writing a compound adjective before a noun, then you would use a hyphen. For example, you would say "a thirty-two-degree Celsius day." Here, the hyphen is used because "thirty-two-degree" is modifying the noun "day."