English grammar. Who vs. Whom - how to understand which word to use

To understand the tricks of English grammar can be quite difficult. A classic example here is the choice between who and whom. Even native speakers do not always correctly use the right word, let alone those who are just learning English.

In the blog of one of the English spelling and grammar checking services, I found material with several rules that need to be used to always correctly solve the Who vs Whom dilemma. Here is an adapted translation of this material.
')

Subject and Supplement

The difference between who and whom is best explained by the concepts of the subject and the addition in the sentence. The subject is used to describe someone who performs the action. If in the sentence you are talking about such an actor, then you need to use who.

In short: “Who” performs actions in your sentence.

Examples:

Who is going to party with me?

Who is the tallest in the class?

Who broke the vase?

If we are talking about someone or something, in relation to whom or what the action is performed, then this is an addition. And then you need to use whom.

Examples:

Whom did she shout at?

To whom your message was sent?

Mnemonic rule

There is a simple mnemonic rule for memorizing, who or whom to use in a sentence. You need to think about how you can replace the actor in a sentence — if the pronoun he or she is suitable as a substitute, then Who should be used. If you can replace only him or her - then you should use whom.

Definition by question

Another way to solve the problem is to ask a question. If the proposal is about someone who performs the action (subject), then you can ask a question with the word who.

Example:

Offer : Tom is going home.

Question : Who is going home?

Conversely, if an addition is mentioned, that is, something that does not perform independent actions, but only “accepts” them, then we can formulate a question with the word “whom”.

Example:

Offer : The letter is delivered by a mailman.

Questions : The letter is delivered by whom? / By whom the letter is delivered?

"M-rule"

Everything can be simplified even more. Understand which word can be used with a single letter M.

Here's how it works: if you answered Him to the question from the item above, use Whom - both words end in M. If you answer He, then use Who. Both words end in a vowel.