A short story is one idea; a novel is a whole soup of them.

A short story is the shortest distance between two points; a novel is the scenic route.

You can write a short story in two hours. Two hours a day, you have a novel in a year.

The driver watched the young female figure approach within his rearview mirror, unable to discern more than superficial characteristics. As she grew closer, he saw the mud streaks and torn clothing, and within her eyes, he saw an emptiness where something beautiful might once have dwelled. A thing not lost, but taken, abruptly and without warning, using method so thorough as to alter a soul.

What can you do if you are thirty and, turning the corner of your own street, you are overcome, suddenly, by a feeling of bliss - absolute bliss - as though you'd suddenly swallowed a bright piece of that late afternoon sun and it burned in your bosom, sending out a little shower of sparks into every particle into every finger and toe?...

A subplot is a distinguishing characteristic of the novel; the short story, for example, does not need subplots.