Package inputenc Error: Unicode character Σ (U+03A3) (inputenc) not set up for use with LaTeX.

Running Pdflatex with math symbols not put inside proper math block can throw this error

Package inputenc Error: Unicode character Σ (U+03A3) (inputenc) not set up for use with LaTeX.

In the above message the sigma symbol is being used outside the math block as shown below. x= Σyi

The solution is to put the equation into the math block, so surround the text with $ symbols and use the sum command which is the latex for sigma.

$x= \sum yi$

The error should not apper now on the usage of pdflatex .