To express 0.5 as a fraction, you can write it as:
\[ 0.5 = \frac{5}{10} \]
Next, simplify the fraction by dividing both the numerator and denominator by their greatest common divisor, which is 5:
\[ \frac{5 \div 5}{10 \div 5} = \frac{1}{2} \]
Thus, 0.5 written as a fraction in simplified form is:
\[ \frac{1}{2} \]