Do we need to change 'and' to 'or' when the affirmative sentence is modified to negative or interrogative?

Question

A grammar rule has been taught in our school, in which when we modify an affirmative sentence to a negative or interrogative one, we should change 'and' to 'or'.

For example:

1. Eat and drink in the metro.

2. Don't eat or drink in the metro.

3. He and I are playing football.

4. He or I aren't playing football.

But I also saw some sentences in which 'and' should not change to 'or' when the sentences are modified to negative/interrogative.

For example,

5. You know French and English.

6. Do you know French and English?

7. Do you know French or English?

8. You don't know French and English. // This one seems not correct.

9. I don't know French or English.

There should be more, but I can not dig out all of them. Appreciate if anyone could provide more here.

So, are there any rules of thumb for this?

Answer 1

After having made some research with the question “Bread, rice and porridge - I don't like them.” how to say? find the summary of the results below.

First of all, if you are looking for a really clean way to express "Bread, rice and porridge - I don't like them (all)." in one coherent clause (not just sentence or a clause with additional backreferences) then there is only one way known to me:

I like neither bread nor rice nor porridge.

I admit though that neither ... nor ... (nor ...) sounds a bit too repelling if you don't intend to emphasize the negation of each item in particular. So, the next less repelling but clean way is to use the enumeration of all items and to refer to it, e.g. with a pronoun, all, or following:

Bread, rice and porridge - I don't like them (all).
Bread, rice and porridge - I don't like (any of) them.
I don't like (any of) the following food items: bread, rice and porridge.

If you are looking for other, shorter, and more colloquial ways then the good news is: there are such ways; but the bad news is: they are ambiguous and therefore dependent on the context and the goodwill of the listener.

1) The or-way

I don't like bread, rice, or porridge.

This way has been said to me to be the conventional way. But technically spoken this way is not quite correct because bread, rice, or porridge refers to at least one from the set { bread, rice, porridge }. So, technically spoken it could have each of the following meanings:

I don't like bread, but I like rice, and I like porridge.
I don't like rice, and I don't like rice but I like porridge.
I don't like porridge, and ...
...

As the listener does not assume the speaker would let him guessing the specific meaning it's only a pragmatic consequence to interpret "I don't like bread, rice, or porridge." as

I don't like bread. I don't like rice. And I don't like porridge.

2) So, why not saying

I don't like bread, rice, and porridge.

Some native speakers say this sentence would mean that I don't like bread, rice, and porridge (mixed) together though I might like bread, I might like rice, and I might like porridge. Other native speakers point out that in the context of bread, rice, and porridge there is no such mix of ingredients, so it would be perfectly understood as "I don't like bread, I don't like rice, and I don't like porridge".

Two examples to show the difference:

I don't like peanut butter and jelly.

would be understood as "I don't like the combination of peanut butter and jelly". Whereas

I don't like Fords, Audis, and Hondas.

would always be understood as "I don't like Fords, I don't like Audis, and I don't like Hondas" as you cannot mix cars together.

---

Coming back to your example, the negation of "You know French and English." could be both

You don't know French and English.
You don't know French or English.

Though, myself, I prefer the clean form in this case:

You know neither French nor English.

Answer 2

I am fairly certain that this is incorrect. And and or convey different meanings, and so either can be correct depending on what you want to express.

For example, it makes perfect sense to say

Don't eat and drink in the metro.

But this implies that you are not supposed to eat and drink at the same time, where

Don't eat or drink in the metro.

prohibits you from doing either of those actions.

Answer 3

The verb will in fact dictate whether you'll use and or or, sometimes using and and or in the same sentence, depending whether the elements are to be added, subtracted, or a divided in the action.

Am I a cat or a rabbit?

I can't be both a cat and a rabbit at the same time.

I am not a cat, nor am I a rabbit, since I bark to speak.

Someone asked me: " Do you like raw fish or carrots tips? I cooked a special dish for dogs, using both ingredients, and although it sounds like it, this dish was not made for cats nor was it for rabbits, or it would smell like it."

Someone asked me if I would rather eat raw fish over carrots tips.

Which do you like better? Is it raw fish or carrot tips?

Is raw fish or carrots tips your favorite?

Are raw fish and carrots tips always combined in your food?

I eat fish and carrot tips. I am not a person nor am I a thing.

I am a pet and the best companion you'll ever get.

I want a pet or nothing.

I want a pet and nothing else.

I love my pet and no one else.

A carrot tip is the tip of a carrot, which is healthy for cats, dogs and of course, rabbits.