Artist 
Writer Golden section or golden ratio
The ratio 0.62 which you can use to divide lines and rectangles in an aesthetically pleasing way. The ratio is approximately the ratio of 1:1.6, 3:5 or 4:7.
3:5 is a useful rule of thumb. You can easily divide the edge of your canvas into eight sections by halving it. Then halve each half, then halve each quarter. Now count three sections and you have a golden section.
See the Composition Building Block for more information.