If a quadrilateral is a parallelogram then opposite sides are parallel. For example, look at the diagram I provided below. If quadrilateral A,B,C,D is a parallelogram, then side A,B is parallel to side D,C. Also, side A,D must be parallel to side B,C.
Hey there! :D So you're wondering how you can tell if a quadrilateral is a parallelogram, right? Well, you are about to find out! The way you can tell whether a quadrilateral is a parallelogram because we know that a quadrilateral has 4 sides, right? And a parallelogram is a figure with opposite sides that never intersect or cross. So for example, a square is a quadrilateral and it has 4 equal sides and if we extend the lines horizontally, the would not cross.
I hope this makes sense to you! Have a good evening!(If you are in the US, but if you aren't, good morning!) :D
