I've been reading a lot of Man from U.N.C.L.E. fic in the last couple of days, and while most of what I've found is very well-written and enjoyable, having just completed another book about grammar, I'm a little twitchy. That being said, three very common mistakes people make with similar words. I want it noted, until this week, "affect" and "effect" were my trouble spot. I think I've got it now.
further/farther
"Farther" is physical distance. Any physical distance at all.
Napoleon stepped farther away from Illya as someone rounded the corner.
"Further" is for discussions.
The THRUSH agent pressed the gun to Illya's cheek. He was obviously not in the mood to further a discussion on whether or not he was a patsy.
affect/effect
99.9% of the time, "affect" is a verb. It means, "to influence."
Illya affected the outcome by shooting the THRUSH agent in the knee.
99.9% of the time, "effect" is a noun.
The effect of Napoleon's charm was always the same: Women swooned. Men grumbled. Illya wondered how Napoleon still had all of his natural teeth.
done/finished
"Done" is, at the basics, applied to making food. It usually stands in for "cooked."
Napoleon was convinced Illya would eat an entire turkey, even if the turkey wasn't done.
"Finished" is used for saying something is complete. It is also used to denote when someone has finished a task.
"Paperwork?" Napoleon asked.
"All finished." Illya replied.
"Then we're finished with the day," Napoleon replied.