What is 0.5 in fraction?

Here's a procedure that works for any decimal:

Step #1).  Read the decimal out loud.
                 Listen to yourself as you read it.

Step #2).  Quickly, before you forget it, write down
                 what you heard yourself say.

When the decimal is 0.5 . . .

Step #1).  Read the decimal out loud.  Say "five tenths".

Step #2).  Write that down.  " 5/10 " .

You may simplify the fraction if you can and if you feel like it.
To simplify a fraction, divide the top and bottom numbers by
their greatest common factor.
5/10 simplified becomes  1/2 .