Is forwards grammatical, or is it backward?

Is it “toward” or “towards”?

“Backward” or “backwards”?

“Afterward” or “afterwards”?

Yes.

Some of you may remember the commercials for 1-800-Mattress. “Leave off the last ‘s’— for savings,” its tagline went.

Well, you can leave off the last “s” for saving face in “toward,” “backward,” and “afterward,” at least in American English.

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Conversationally, it doesn’t matter. In journalism, though, every style guide wants you to leave off the “s.” Why? They don’t say: The entries in the Associated Press Stylebook and The New York Times Manual of Style and Usage are straightforward: “afterward (not afterwards),” the Times entry says in its entirety; “toward Not towards,” the AP’s says.

RELATED: Your copy will blow if you overuse this word

The Chicago Manual of Style is a little more discussive. In a section written by the language maven Brian A. Garner says this:

The preferred form is without the -s in American English, with it in British English. The same is true for other directional words, such as upward, downward, forward, and backward, as well as afterward. The use of afterwards and backwards as adverbs is neither rare nor incorrect. But for the sake of consistency, it is better to stay with the simpler form.

No one really knows why “toward” and its s-less cousins became more “correct” in English, but it happened in the late 19th century. As the Merriam-Webster Words At Play blog notes:

The word toward(s) is old: it goes back to the 9th century, where it was a blend of the word to and the suffix -weard, which was used to refer to a specific direction. … But from the earliest moment of toward’s life, it was spelled both with a final -s and without. This is a bit odd, since the Old English of the 9th century was very particular about its case endings, but it appears that this was fairly common when it came to direction words in Old English: just about every -ward word from this era that was formed with an adjective, adverb, or preposition—forward, backward, froward, inward, outward—has an analogous -wards mate that is almost identical in meaning.

In 1867, Edward S. Gould wrote a rather supercilious book on all the “mistakes” in English. As the M-W blog says, “Gould quotes a bit of (not entirely spurious) etymology, notes that the Old English -weard has given us a number of words, and then claims that the addition of -s to these words is an ‘innovation’ without merit.”

That did it for many people, who dropped their “-s” endings with abandon.

Look back, though at Chicago’s reference: “The use of afterwards and backwards as adverbs is neither rare nor incorrect. But for the sake of consistency, it is better to stay with the simpler form.”

That throws a monkey wrench into the argument that all these words are identical, especially in British English. As the Grammarphobia blog says, “In British English, there’s a slight difference between ‘forward/backward’ and ‘forwards/backwards.’ The words in the first set (those without the ‘s’) are used as adjectives (‘forward motion,’ ‘backward glance’), while the others (with the ‘s’) are used for the most part as adverbs (‘move forwards,’ ‘run backwards’).”

1-800-Mattress filed for bankruptcy in 2009, but not because it left off that last “s.” You should leave it off when you’re writing for a more formal audience or adhering to journalistic style. But there’s nothing untoward about using “towards” in ordinary conversation. You’re just being colloquial, not backwards.

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Merrill Perlman managed copy desks across the newsroom at The New York Times, where she worked for 25 years. Follow her on Twitter at @meperl.