Hi again Lost Soul, These three sentences begin with what we call modal verbs, which are a subset of the auxiliary verbs. Modals are concerned with ability/inability, possibility/impossibility, necessity, obligation, polite suggestion, condition, etc. "Can" is used for ability, to indicate the past tense of "can," and at the beginning of polite questions: "Could" you please pass the salt? "Would" is used for possibility and in conditional statements, such as "if, then" constructions.

No difference at all except that the second two are considered a bit more formal. But all are perfectly polite and will get you the salt 🙂

All of these will result in you receiving the salt from the party you asked the question to if they want to help you. However, most Americans are very fond of lame jokes. 9/10 times if you ask an American, "Can you please pass the salt?" They will reply, "Yes." and then stare at you. It's a joke. They "CAN" pass the salt, but it doesn't mean they will. "Can you ..." is asking if someone is able to, or has the capability to do an action. "I don't know, can I?" is another popular, and lame, joke. "Could you please pass the salt?" might result in a similar situation. They might hand you the salt, or they might respond, "I could...." The use of the word "could" sometimes encourages people to make a trade. "Could you please pass the salt?" "I could if you gave me your dessert." I'm not saying this will happen, but it does often happen. People see an opportunity because they have what you want, so they become interested in benefitting from the situation. The best way to defeat this type of jokester, is to stare at them with one eyebrown raised. Eventually, they'll give you the salt without a trade. Probably... "Would you please pass the salt?" is a request for an action to be done. It is not a question of can it be done. This is more likely to result in you getting salt from the person. "Could" and "Would" do sound a bit more formal, but that's not always a good thing. Sometimes it's better to just be succinct (to the point). If you had the salt and I wanted you to give me the salt, my request would sound like this: "Salt, please." The context is obvious. The request is simple. I am still polite. and, I get the salt.

The difference is courtesy. The order in which you wrote them goes from least polite ("can") to most polite ("would"). The reason that "would" is the most polite is that it asks nothing about the person's ability to pass the salt. It is merely a request that the person consider passing the salt. The reason that "can" is the least polite is that it asks if the person is able to pass the salt. You need to say it this way when the salt is located on the table in a position where the person might not be able to reach it. It is never actually impolite to say "can you pass the salt", just less courteous.

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