In the 1700s, Garner’s Modern American Usage says, Samuel Johnson declared an end to “wont.” But, Garner’s continues, “it hangs on today as a slightly whimsical way of expressing customary behavior.” It also hangs on as a misuse of “want.”
“Wont” has to do with habit or custom; “want” has to do with desire. But when something is a habit, it’s often something you want to do, so confusion erupts. “He wants to go to the baseball game on Thursday, as is his wont” means he desires to do what he is accustomed to doing.
In that example, “wont” is a noun. In its most common form, “wont” is a predicate adjective, meaning it is closely accompanied by a “linking” verb, usually an infinitive, as in “He went to baseball game on Thursday, as he is wont to do.”
One clue that you desire “want” instead of “wont” is that, while “wont” can be a verb, it is rarely used that way; if you want a verb, it’s probably “want.” For its part, “want” can be a noun, as in “his greatest want is to go to the baseball game on Thursdays,” but it’s not accustomed to being used as one.
“Wont” first appeared as an adjective in the late ninth century, from Old English words for “to stay habitually, dwell, live (in a place or with some one),” The Oxford English Dictionary says. It has gone through many iterations to reach the “whimsical” stage Garner’s gives it; many people think it just means “desire.” You, though, should get into the habit of avoiding the use of “wont” to mean “desire”; Garner’s says it’s only at Stage 1 of the five-stage Language-Change Index, still a mortal grammatical sin.
Of course, a spelling checker will not stop on “wont,” even if you might “want” it to (unless you put it in your personal spelling dictionary). And these days, using “wont” instead of “won’t” for the contraction of “will not” shows up all too frequently in texting, SEO keywords, URLs, and other places where an apostrophe just gets in the way. The 1994 edition of Merriam-Webster’s Dictionary of English Usage says that “confusion of wont with won’t has been warned against on occasion, but we have no evidence that such confusion has ever actually occurred.”
Twenty years later, you “won’t” have to look too far for such confusion, if you “want” to make that your “wont.”