Wow, this is the one thing I know about in biology
A dicotyledon plant is broad, and have a 'network' of veins.
<-- this is a picture of one so you know what I mean.
A monocotyledon is the opposite. They are long and narrow, with very straight veins. The veins are parallel.
<-- There is a picture of one so you know what that looks like too.
Hope this helps, and that you manage to see it