That "e" can also magically change a word into another form, such as a noun into a verb. This being illogical English, there are few "rules" as to what it does, though.
Let's start with the easy ones. When you take a "bath" (noun), you "bathe" (verb). A baby just getting "teeth" (noun) is starting to "teethe" (verb). When you take a "breath" (noun), you "breathe" (verb). Almost no one gets those wrong.
Now, let's throw a spanner in the works. Take the noun "swath." It's a path, as in the "swath" of grass cut by a mower. It means a strip, but usually a strip cut into something else: a "swath" of land; a wide "swath" of destruction; a "swath" of bandages around a head wound. Not so fast: That "swath" of bandages is really a "swathe" of bandages. "Swathe" is a noun, too, for strips or lengths of "cloth" that, um, "clothe" something. That teething baby is bundled in "swathes" of blanket. The vowel sound in "swathe" sounds like "sway" while the one in "swath" sounds like "swat."
But "swathe" is a verb as well. You "swathe" the injured person's head with "swathes" of gauze. Possibly because "swath" and "swathe" are so close in meaning, they are confused on occasion, sometimes by people who think "swathe" is fancier than "swath." (To be fair, "swathe" is correct in some dialects for "swath" as a path.)
"Sheath" suffers a similar confusion. The knight returning his sword to its "sheath" would "sheathe" (verb) it. But "sheathe" is becoming rarer, as people forget that poor "e" and use "sheath" as a verb as well. It has crept to Stage 2 of the five-stage Language-Change Index in Garner's Modern American Usage, still wrong, but less noticeable after people have had a few.
Then we have "loathe." It's a verb meaning "detest" or "hate." If you hate to do something, you are "loath" to do it. No "e," and "loath" is an adjective here, not a noun. The misuse of "loathe" as the adjective is at Stage 3 in Garner's, meaning even some sober people might not notice, though it's still not standard English.
"Loath" is also spelled "loth," but since most dictionaries list that as a "variant" spelling, you should be loath to use it.
Merrill Perlman is adjunct assistant professor at the Columbia Graduate School of Journalism and president of Merrill Perlman Consulting, offering consulting and freelance editing services and training in journalism, grammar and usage. Among her clients are The New York Times, ProPublica and the Poynter Institute. She writes the "Language Corner" column and blog for Columbia Journalism Review. Merrill retired in June 2008 after 25 years at The New York Times, most recently as director of copy desks with responsibility for managing 150 copy editors.Click here to read other articles by Merrill Perlman