Your spellchecker won't help you.
When I'm not hammering commas into all interstices, or complaining about them in splices, or the occasional possessive apostrophe, I spend a fair – no, actually a completely unfair – amount of my
critiques time bullying homophones. I should probably have left this article to the bear, who specialises in them (generating them, that is, rather than correcting them) but since he doesn't seem to have seen fit…
The English language developed from a marriage between two indo-european roots, already polluted with Celtic and Scandinavian influences, one Germanic and one Latin based, and spent the next nine hundred years steal – adopting extra words from any other languages it came in contact with, or, when all else failed, inventing new ones.
Which explains why it is the most flexible, diverse and synonym-rich means of communication on the planet, but also why its spelling is frequently somewhat illogical, and the fact that a number of sets of words, coming from different origins by convergent evolution, can sound exactly the same while having completely different meanings.
Which is fine when they're {there, their} spelt the same; but this is not always the case.
I'm not going to attempt to point out all of them; the list at
http://www.bifroest.demon.co.uk/misc/homophones-list.html has over four hundred and forty groups (and misses "canon–cannon", which leaves me wondering if I have been pronouncing one of them incorrectly for years, or should be checking for other oversights, or citing othersites), most of them pairs/pears/pares, but some triples and quadruples, but draw attention to the more common reoffenders. I suspect anyone who chooses to use the word "caul", for example, is not going to get it confused with "call".
Probably the most common (and illogical enough to be accepted as an example of English grammar) is the possessive "its" that lacks the apostrophe, "it's" being reserved for contractions (usually "it is", but occasionally "it has"). "Whose/who's" is the same case, but less frequently used. Then "your/you're" (we won't bother about "yore" or "yaw" right now), which at least one long-term Chronite has not yet mastered (or possibly doesn't know where the ' key is [difficult if you keep changing keyboards]) Everybody's missed a "to/two/too" at some time, and I own up to having posted a "hear" for a "here"; your fingers know the word exists, your eyes and spell checker say it's spelled wright; and, of course, it is. Its just knot thee write whirred. two bee shore. (Hmm, they didn't get "shore/sure/Shaw", either, nor "whirred"),
For some reason "peek", a sly glance, and "peak" the top bit of a mountain get frequently confused, as do "through" and "threw" (how did those end up sounding the same?).
Not all of the problems are genuine homophones, of course; sometimes they don't even sound the same. Using "then" for "than", for example, or "where" (in which location, homophones wear and ware) for "were" (past tense plural of the verb "to be – yes, I know, but technically "you" are plural and "thou" art singular – which nobody would spell "whirr"). Or the use of of "of" instead of "have" when decontracting "would've".
We are politely tolerant to Hope as she bakes flower (or doesn't bawl) (it's all right, I asked permission to take the mick) but I wonder if any of us really understand what it must be like not having that little flash of "that's not right" light up behind our eyebawls? (well, possibly not all like me, where it can dazzle out a fair percentage of reading). And we all do it, anyway. Hey, word processor developers, how about a "this is in my homophones directory, highlight and click on it and you get dictionary function telling you what the word means" as is in my Kindle? A whole lot more use to writers than some of your grammar rules and the like.
Postscript:- "Chute/shoot", and what are they doing with "cymbol" for "cymbal"? "Passed" and "past" give regular problems, "pray/prey", and I've seen "warred" written as "ward". No, this list I've come up with is not adequate.