What's the difference between a summary and a synopsis?

My English professor is very meticulous, and I will fail if I don't get this right. I wrote what I thought were great summaries on several essays by Henry David Thoreau, but he glanced over my work and told me that they were not summaries. I wrote synopsis instead of summary, apparently. I've researched it, and I... show more My English professor is very meticulous, and I will fail if I don't get this right. I wrote what I thought were great summaries on several essays by Henry David Thoreau, but he glanced over my work and told me that they were not summaries. I wrote synopsis instead of summary, apparently. I've researched it, and I can't find the difference. I'll paste what he called a synopsis below and hopefully you guys can help me figure out the difference.

“A Plea for Captain John Brown”
Thoreau asserts that John Brown’s actions against slavery and injustice are exemplary because he acts as men should, with a conscience, and acts according to utmost moral standards and personal convictions. And of the people who condemn his actions, Thoreau maintains that they have no right to judge his principles, for they are not even his peers to do so, nor do they act on their principles themselves. Brown, Thoreau claims, is a man who has truly lived, for his actions were not motivated by any earthly, personal gain or advantage; rather, his cause was one of principle—of a higher good.
4 answers 4