Vinegarette vs. vinaigrette
Wrong: I’d like vinegarette dressing on my salad.
Right: I’d like vinaigrette dressing on my salad.
Although frequently seen, this is a simple misspelling/mispronunciation (vin-uh-ger-ETTE) of the French word vinaigrette (vin-uh-GRET or VEEN-uh-gret), based on confusion with vinegar, which is often (but not always) a principal component of the dressing.
Principal vs. principle
Wrong: He refused on principal.
Right: He refused on principle.
A principal (noun) is something or someone of foremost importance (for example, a school principal or a meeting among the principals in a transaction). It can also be used as an adjective (the principal reason for something). A principle (noun-only) is a rule of conduct or action, or a doctrine or tenet, among other meanings.
There are plenty more words of this type to go, so stay tuned for the next installment.