How and when to use 'whom' instead of 'who'
Wired recently came out with a study of dating site profile factors that correlate with greater success, and guess what: that girl who you're trying to impress is more likely to go for you if she's that girl whom you're trying to impress. Yup, use of whom in a guy's profile correlates with 31 percent more contacts from the opposite sex.
Why would use of whom matter? Presumably because it's associated with more intelligent use of grammar, and it turns out that women tend to value intelligence in men. But if you're going to use whom, you have to use it correctly. You can't say "Whom is going with you?" because she might know that that's wrong.
The problem here is that most of us do not use whom in regular speech. It's no more natural to most modern English speakers than the proper use of –eth conjugations and thou pronouns. It's almost a foreign word. It just seems like who with a bowtie on it.
Here's the simple rule on where to use whom rather than who: Every verb that is conjugated (e.g., I kiss, She kisses) has to have a subject: I kiss her, She kisses me, I want to kiss her, She is kissed by me. The rule is that you use who when it's the subject and whom when it's not. So look around at the conjugated verbs in the sentence. Are all their subjects spoken for? If so, use whom. If not, look for which one the who is the subject of just to double check, and use who. Think: "Subject? Oo. Object? Mm."
For those who aren't always clear on what the subject of a verb is, here are a few other ways to think about it.
If it's in a question, and the answer could be him or her, use whom; if the answer could be he or she, use who. "Whom are you kissing?" "I'm kissing him." "Who is kissing you?" "She is kissing me."
If it's in a relative clause (a sentence embedded in another sentence), look for another noun or pronoun between who(m) and the verb. If there is one, that will be the subject and you should use whom: "She is the person whom you are kissing." If there isn't one, who will normally be the subject: "She is the person who is kissing you."
If it's after a preposition (to, from, for, of, by, etc.), use whom: "You are the person to whom I am speaking"; "She is the one for whom I bought the lip gloss"; "From whom did you get that idea?" But see below about whomever for an exception.
If there's a clause introduced by a verb about thinking, saying, believing, or something like that, look very carefully to see what the subject of the clause is. Take for example "Who(m) did you think kissed her?" There are two conjugated verbs: did and kissed (think is an infinitive). The subject for did is you. What's the subject for kissed? Not you – it's taken by did. Not her – it's the object of kissed. No, it's who: "Who did you think kissed her?" Don't bother saying "It has to be whom because it's the object of think." The actual object of think is the whole clause "who…kissed her."
So now try "Who(m) did she say he kissed?" What are the conjugated verbs? Did and kissed. What are the subjects? She and he. We don't need another subject. So it's "Whom did she say he kissed?"
The rules for how to use whomever are the same as for whom: Subject? Oo. Object? Mm. There is a bit of a risk of getting fooled by a preposition, though. Look at a sentence such as "I'll give a kiss to who(m)ever wants one." You see the to and may think, "OK, preposition before, so it must be whomever." But no! Look at that verb wants. What's the subject? It's whoever. But the complement of a preposition is always an object, so why is it not whomever? Because the whole clause is the complement: "I'll give a kiss to [whoever wants one]." Of course if something else is the subject of the verb, you use whomever: "I'll give a kiss to whomever I like."
Now, then. Let's look at all the whom examples above and see if any of them are confusing if we just leave the bowtie at home and use who or whoever: "Who are you kissing?" "The person who you are kissing." "Who did she say she kissed?" "I'll give a kiss to whoever I like."
Uh, yup. Every one of them perfectly clear. Generally less stuffy too. So is that extra m just a torture device like a too-tight collar and hard-to-tie bowtie?
Here's why we have it. English nouns used to have a thing called case inflection. What this means (in simplified terms) is that every noun would have different forms depending on whether it was subject, direct object, indirect object, or possessor (or source), for singular and plural. Many other languages have this — German and Russian both do. It was sort of like if we were to add –em to all objects: "Mary kissed John-em" and "John kissed Mary-em" — we could change the order and it would still be clear: "John-em kissed Mary" would mean Mary was the kisser and John the kissee.
But over the centuries we simplified all that. Now the only difference for normal nouns is that we have –s for possession and for plural (we use an apostrophe to mark the difference in writing, but of course we say them the same). Instead of marking the grammatical relations between words that way, we just use word order, which has to be more consistent as a result. But we kept some of the difference for pronouns: We have to say "He kissed her" and not "Him kissed her" or "He kissed she." We generally manage to keep this straight, and even though it rarely actually adds clarity we stick to it because it's what we do. We kept it from before. It's a family heirloom.
Well, whom is like him: it's a family heirloom (and a pronoun). It's one of those heirlooms that don't get used very often. Most of us bring it out just for special guests and fine company. So we're not very used to it. But it's still useful — for signifying that we're treating the other person like fine company. It's something you can use to dress up your language. And, as ZZ Top says, every girl crazy 'bout a sharp dressed man.