A ground grown grain, that is full of starch... NOT a VEGETABLE! And, NOT a starch.
In history corused to be part of a weed called "Teosinte". It was very small, and barely eatable. This was usually grown in cetural america.
This later evolved in the what they called "Maize", what we now call early maize. It would be large enough to eat, and was used in replacement of the vegetable.
Now we know corn as the modern maize. The normal crop rage from 6-12 inches long, and 2-5 inches wide. The corn is on waht we call a cob, and the corn grows around it taking the nutrience from the cob. I has become a normal dish in our would today.
Person 1: What vegetable do you want for dinner?
Person 2: Let us have a grain instead, we can have corn! I need to have some starch anyways.
Person 1: Would you like to eat the corn off of the cob, or cut if off first?
Person 2: All the same to me.