Why would you define font-weight in numeric value instead of plain words?

Some fonts have a multitude of very specific weights such as: 'light', 'extra-light', 'thin', 'semi-bold', 'bold', 'extra-bold', 'black', etc. It's easier to describe the difference between light and thin in numbers than to assume everybody understands the difference between them if you put it in words.

Having said this most fonts only have a couple of weights. In that case it's just as easy to just say 'bold' instead of '700'.

Numeric values would allow you greater precision. But the word choices are often good enough, and they do tend to be more commonly used.

Thanks for replies! So when it comes to our exercise I've pasted below (tell me if I understand it correctly), it doesn't REALLY matter how you name font-weight? Even if font real weight is 300, and you name it 700, font still remains 300, right?

@font-face { font-family: 'Open Sans'; src: url('webfonts/OpenSans-Light-webfont.eot'); src: url('webfonts/OpenSans-Light-webfont.eot?#iefix') format('embedded-opentype'), url('webfonts/OpenSans-Light-webfont.woff') format('woff'), url('webfonts/OpenSans-Light-webfont.ttf') format('truetype'), url('webfonts/OpenSans-Light-webfont.svg#open_sanslight') format('svg'); font-weight: 300; font-style: normal; }