who vs. whom

This is tricky, but once you know the rule it seems much less complicated.

Who or whom is usually used in a question, for example:

Who goes there?

The rule:

If the answer to the question can be "he" (or she); use who. If the answer can be "her" (or him); use whom. For instance:

Who goes there?

He does.

For whom does the bell toll?

It tolls for her

Check out the grammar and spelling assistance metanode.

It's really very simple, and I don't see any reason why I should see node titles like Who to send presents to, and when.

Forget indirect pronouns and other things you never learned about in 3rd Form Grammar. The simple rule is this: When you would answer him (ends with an "m"), use whom. When you would answer he (doesn't end with an "m"), use who.

How simple is that?

Examples:

• _________ am I going to see tonight?
  I am going to see him, therefore you need a whom.

• _________ cares how pretty your girlfriend is?
  He does, so you need a who.

• ________ to send presents to, and when.
  I'll send him a present. So it should be a whom.

• ________ is this book about?
  The book is about him. It's whom again.

As a follow-up, anyone familiar with the German language should find this simple. The use of 'whom' is in the Accusative (Akkusativ auf Deutsch) case. When one would use 'mich' instead of 'Ich', 'dich' instead of 'du', 'ihn' instead of 'er', and so on (und so weiter), you use 'whom' (or 'wen', in German).

Same with the dative (Dativ auf Deutsch) case (To whom, or 'wem'). Since this is quickly turning into a treatise on German grammar, I shall quickly stop, as German speakers no doubt should be familiar with to him (ihm), to her, to it, etc.

So, in summary - if it's accusative or dative, it's whom, or to whom, respectively.

It depends on whether it is the subject or object. The distinction can be seen with these useful examples:

It is unlikely that you'll ever meet anyone who really cares whether or not you ever say "whom" again.

It is unlikely that you'll ever meet anyone to whom it matters whether or not you ever say "whom" again.

Sud makes a good point, and it's not merely an issue of the populace in general not caring; most professional/academic linguists would agree here that using 'who' as the object term is not Bad and Wrong. The assumption that 'whom', a term not employed by the majority of English speakers, should - under the circumstances so eruditely recorded by Footprints and Xemorph - be more correct than the use of 'who' would be, and that people who prefer to use the latter are somehow misusing the language, is a basically flawed one.

The 'correct' way of saying or writing something is not necessarily the way that people said or wrote it fifty years ago. There is no decay of language; only evolution. More recent editions of many dictionaries list 'whom' as rarely used, implying that in some cases it may be entirely obsolete.

I love pedants dearly - I have to, I'm British - but it gets to the point where we have angry letters to newspapers complaining that kids these days are saying 'orchard' instead of the (obviously correct) 'ort yard', what is the world coming to, signed Disgusted of Tunbridge Wells. Without this kind of evolution, English wouldn't be the amusingly illogical hybrid that it is today.

And since it is now, as one will note from scanning through most modern literature, an endangered species, I feel it my duty to state that no whoms were harmed in the production of this node.

Who and whom are both interrogative pronouns (used to ask questions) and relative pronouns (used to refer to a noun or pronoun in the main clause).

Ex:
Who is going? (interrogative)
Mr. Peabody is the one who is going. (relative, referring to one)

These pronouns may be either singular or plural in meaning.

Ex:
Who is noding? (singular)
Whom do you prefer for these jobs? (plural)

Who (or whoever) is the nominative form. Use who whenever he, she, they, I, or we could be substituted in the “who” clause. (If in doubt, rearrange the clause as demonstrated below.)

Ex:
Who is filling the nodeshell? (She is filling the nodeshell.)
Who shall I say is calling? (I shall say he is calling.)

Whom (or whomever) is the objective form. Use whom whenever him, her, them, me, or us could be substituted as the object of the verb or the object of a preposition in the “whom” clause.

Ex:
Whom did you see today? (You did see her today.)
To whom were you /msg-ing? (You were /msg-ing him.)

This is a help/revision sheet I made a year ago for my English as a foreign language students. I hope it is useful.

The difference between ‘who’ and ‘whom’

• Essentially, ‘who’ is the nominative case, and ‘whom’ the accusative

• Therefore, when the person to whom you are referring is doing the action in the sentence, use ‘who’, and when said person is having the action done to them, use ‘whom’

For Example:

• Tomas is a boy whom I like very much
• Tomas is a boy who likes me very much (I hope!)

• Use ‘whom’ as the object of the sentence, or after a preposition (by, with, to, etc.)

(this section was intended to be a table, but I was unable to do one in HTML. So I have put the three columns of the table in order and numbered the rows. I hope it is comprehendable)

Correct
1. To whom (was it done)?
2. By whom (was it made)?
3. From whom (did you hear that)?
4. For whom (is that gift)?
5. She is the girl whom I love
6. She is the girl who loves me
7. To Whom It May Concern:
(a traditional letter-opening)
8. Who ate all the pies? David did!


Incorrect
1. Who (was it done) to?
2. Who (was it made) by?
3. Who (did you hear that) from?
4. Who (is that gift) for?
5. She is the girl who I love
6. She is the girl whom loves me
7. To Who It May Concern:
8. Whom ate all the pies? David did!


Reason
1. After a preposition (To)
2. After a preposition (By)
3. After a preposition (From)
4. After a preposition (For)
5. ‘She’ is the object of the sentence (she is being loved)
6. ‘She’ is the subject of the sentence (she is loving)
7. After a preposition (to)
8. David is the subject as he is doing the action (eating the pies)

(table ends here)

• An easy way to know which one to use is to think to yourself – “Am I saying ‘he’ or ‘him’?”. If it is ‘he’, use ‘who’, and if it is ‘him’, use ‘whom’.

For Example

• He (David) ate all the pies = David is the one who ate all the pies
• I hate him (David) = David is a boy whom I hate

• She (Natalie) is pretty = Who is pretty? Natalie is!
• I love her (Natalie) = Whom do you love? Natalie!



Important Note –

Many people do not know these rules, and consequently do not use ‘whom’. Furthermore, it often sounds pretentious and forced to use ‘whom’ in everyday speech (e.g. people would look at you funny if you were to say “From whom did you get that money?”, even though it is correct. In everyday conversation it is better to say “Who did you get that money from?” even though it is incorrect. Save ‘whom’ for formal speech and writing like interviews, speeches and essays, where it will really impress.

A descriptivist view, or what actually happens

The most common current patterns of usage for "who" and "whom" in most "standard" English speech have diverged from the traditional grammatical distinction between "who"=subject and "whom" = direct and indirect object, described in various other writeups here. In practice, in any but the most formal sorts of speech and very frequently in writing, the situation for both the interrogative and the relative personal pronouns is that:

1. "who" is universally used in subject/nominative roles ("Who ate all the pies?") as an interrogative pronoun, and almost universally - except for occasional instances of hypercorrection - when it is a relative pronoun ("I met a man who ate all the pies.") regardless of register.
   
2. "whom" is generally used for an indirect object where it follows a preposition ("By whom were all the pies eaten?", "I met a man by whom all the pies were eaten") BUT this structure is marked as having a relatively high register, particularly where it appears at the beginning of the sentence or clause. Using "who" here will sound weird/wrong to most standard English speakers, as there is seems to be clash of register.
3. The preposition that governs an object pronoun in such a case can alternatively be moved to the end of the clause, in which case "who" is almost always used ("Who were all the pies eaten by?", "I met the man who all the pies were eaten by"). This structure may be considered "incorrect" by people who follow a prescriptivist tradition, but is absolutely unremarkable in speech. Although it would in theory preserve the subject/object distinction, the use of "whom" in this structure is very rare, possibly because most people who might otherwise use it are also swayed by the Latin-influenced prescriptivist "rule" against using a preposition at the end of a sentence, and hence prefer the more awkward form described in point 2. People who are learning English as a foreign language or otherwise being tested on their English might want to be wary of using this form in examination conditions in case they meet prescriptivist examiners, but it is however the most "natural" sounding structure in real life native English speech.
4. Similarly, when a direct object pronoun appears at the beginning of an interrogative clause, "whom" is considered correct by prescriptivists but "who" is almost always used in speech ("Whom did you meet?" versus "Who did you meet?") and quite frequently in writing. The use of whom is probably more common as a relative pronoun ("This is the man whom I met") than in questions.  For learners, the same caveats as point 3 apply. Note that even people who use the "for whom" indirect object structure are quite likely to use "who" in a sentence-inital direct object position (cf. the Mojave 3 album Out of Tune which includes tracks called "Who do you love?" and "To whom should I write?") 

When who/whom is used as a relative pronoun, interactions with phrasal verbs seem to be problematic. "This is the child whom I brought up" is a trifle awkward; *"This is the child up whom I brought" is wrong (phrasal verbs just don't do that). "This is the child who I brought up" would again be the most natural sounding form, but if you are scared of pedantic teachers/examiners/downvoters or the Microsoft Word grammar checker, you are probably best off using "that" or "which" instead (although that opens up a whole new kettle of fish).

The derived form "whomever" (although possibly not the legalese "whomsoever") seems to be more of an endangered species than "whom" tout court; "whoever" is more likely to be heard in its place even from ardent whom-ers. 

As there seems little scope for ambiguity resulting from the use of "who" in these cases - after all, nouns and the relative pronouns "which" and "that" work perfectly well in English without inflected forms for subject and object - it suggests that the need to distinguish subject and object via different forms is not particularly strong, and may be likely to fade away further in the future.

Although these points all suggest that "whom" is used more and more rarely, it should also be noted that hypercorrect use is quite common by speakers/writers who are seeking to raise their register and are aware of the prescriptivist rules but do not actually know them, particularly the use of "whom" for a relative pronoun which is the subject of the subordinate clause (?"I met a man whom ate all the pies"). I'm a descriptivist so I can't tell you not to do that, but don't do it anyway.

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For reference, the author talks and works in a mostly southernish sort of British English, which probably colours the above writeup, but is not wholly unfamilar with a wide range of other local and distant variants both "standard" and otherwise. He accepts no responsibility for dropped marks, downvotes or black eyes you may receive as a result of following this advice, but would be interested to hear about them all the same.