You need to see an optometrist for this. It may just be the nature of your prescription but straight lines appearing bent can (very rarely so please don't panic!) be symptom of an eye condition called Macular Degeneration. Most common in older people, this condition has the power to destroy sight if it isn't caught early enough and damaged cells will never regenerate.
An anorthopia is an existence of a defect of vision in which straight lines appear to be curved.
straight, angular lines
A Circle
It may be that you were seeing pin cushion distortion; if you wear glasses then the lenses in the glasses aren't perfect and straight lines may appear slightly curved.
An apeirogon. Apeirogons are degenerate polygons that probably appear as never ending straight lines
Straight lines.
A polygon is a two dimensional shape bounded by straight lines. The moon is neither a plane shape (though it may appear as such), and it is clearly not bounded by straight sides.
you draw straight lines with a ruler
They do not - not if you draw them as straight lines.
there are 5 straight lines
This appeared in 'Who moved my cheese' by Spencer Johnson. These lines are by A. J. Cronin
Straight lines that never cross are called parallel lines.