Questions about the word “Both” in negative sentences

You're right. The book is wrong. It's the same as saying "both my brothers hate birds".

"Both my brothers don't like birds" would absolutely mean the same as "Neither of my brothers don't like birds", but I would expect the latter to be used in most cases. If it began with "Both.." I'd expect the construct to be "Both my brothers dislike birds" or similar. I cannot see any interpretation in which "Both my brothers don't like birds" means "One of my brothers likes birds, but the other doesn't".

I can't read the Chinese to know what they intend to convey but "Both my brothers don't like birds" is indisputably saying that neither one of the brothers likes birds. They both do not like birds. Both brothers don't like birds. Neither is pretty much the same - but has a very slightly different use. It's usually in response to a question to select one. For example: \- Which one of them likes birds? Neither like birds. \- Do either of them like birds? Neither one likes birds. \- Tell me which of your bothers likes birds. Neither of them like birds.

"Both my brothers don't like birds" COULD mean that one brother likes birds and the other doesn't, but outside of a specific context, most people would not interpret it that way. Most people would assume that neither brother likes birds.

Your assumption is correct.

Omg. The cram school I teach at (in Taiwan) literally uses this book. (I’m one of the teachers there). Yeah when I came across this part and found this weird as well. “Not both my brothers like birds.” But is this correct? I understand what the textbook is saying - Only one of my brothers like birds. But in reality is it right?

"Both my brothers don't like birds" sounds really awkward to me. It's understandable, but I would never say it like that. ***"Neither of my brothers like birds."***

Both don't like birds = neither likes birds. You're right.

Both the sentences either with 'both' or with 'neither' make complete sense. Using 'both' in this context would mean that you're specifying that you have only two brothers. 'Neither' however, can mean and be used for any number of brothers.

Neither of my brothers like birds. Way more natural sounding. Your book is misguiding you.

The English translation of the first sentence is wrong. It’s supposed to be “My two brothers don’t both like birds”. The correct translation is equivalent to the second sentence. The original English translates back to 我两位哥哥都不喜欢鸟

"both brothers don't live birds" = "neither brother likes birds" People would normally say "neither brother likes birds." That sounds more normal.

When speaking, the average English speaker would interpret that sentence to mean that there are two brothers. Out of those two brothers, you will not find a bird liker. However, technically, the sentence is still true as long as you don't have 2 bird likers among your two brothers. Thus, one brother could like birds while the other doesn't. In this case, both brothers don't like birds. This interpretation is less common, so try not use it.

`BOTH of my brothers DON'T LIKE birds` and `NEITHER of my brothers LIKES birds` are essentially the same thing (the first one could mean they specifically DISLIKE birds, instead of just not caring at all). What you should not say is `NEITHER of my brothers DON'T LIKE birds` because that would be a double-negative, unless you actually mean that BOTH brothers DO like birds.

I think the first sentence should have been written as "My brothers don't both like birds". Which is still awkward but gets across the idea that they do not agree about birds.

I believe what they mean is that “both don’t like birds” does not necessarily mean that neither of them like birds, it only means that they don’t BOTH like birds. One of them could like birds and that statement is still true, both do not like birds. Like a NAND gate if anyone happens to be familiar with logic circuits

Neither of my brothers like birds.

Example 2, the second line in English could be rewritten using the not... Both.. format and mean the same thing. "One brother likes birds and the other doesn't." Has the same meaning as "Not both of my brothers like birds." But again, follows the "not... Both..." Sentence structure. Hope this helps.

“Not both of my brothers like birds” can mean that one of them likes birds but the other doesn’t .

I like birds

我兩位哥哥並非都喜歡鳥 doesn’t necessarily mean neither of them like birds tho. It is more like saying the statement of “both of my brothers likes birds” is wrong. That’s why the OP put a “not” before the “both of my brothers likes birds”, resulting “not both of my brothers likes birds”. But if you don’t say “not both”, then how would you phrase it in a precise way?

"My brothers don't both like birds." = One likes birds, one doesn't. "Both my brothers don't like birds." = A strange sounding sentence that I would interpret as nobody liking birds.

i’d like to point out that in old/poetic english, this can be correct. famous quote: ‘all that glitters is not gold.’ this is a weird sentence, and, in more familiar english, it means ‘not all that glitters is gold.’ but i’d also say that ‘both’ is worse than ‘all’ in this context. and it’s certainly not immediately understandable. the example sentence means ‘neither of my brothers like birds.’

超好笑 我記得我國中的時候小考幾乎每題錯的都能凹 教科書有問題基本上算常態了 不能什麼都相信

It should say “neither of my bros like birds” instead of “both”.

It is *technically* correct, I guess, but it's a very, *very* misleading way to phrase it which no one would ever use unless they were deliberately trying to be misleading. Everyone would take it to mean that neither brother likes birds. Another way it could be phrased with the same words while being easier to understand is "My brothers don't both like birds." it makes it clear that 'don't' is negating 'both', rather than 'liking birds', if that makes sense. 'Both' can absolutely be used in a negative sentence. It's like saying "all birds are not ducks" (still kind of weird phrasing, but this is a structure you might see on occasion, especially in older literature). That doesn't mean that *no* birds are ducks, just that some aren't. That's the important take-away from the lesson; that when a quantitative noun is negated, the statement might still be true for part of the set.

“Both my brothers don’t like birds” is actually meaningless and highly ambiguous. It could mean they both don’t, OR one of them does. So it’s just a shitty sentence.

You are correct. "Both my brothers don't like birds" = "Neither of my brothers likes birds." The word "both" *can* be used in negative sentences, but it usually shouldn't be. "Neither" is a better choice.

Okay, in a mathematical/logical sense, "Both \[of\] my brothers don't like birds" has a meaning that includes both: \* Neither of my brothers likes birds \* One of my brothers likes birds, but the other doesn't The only thing it cannot mean is that both of the brothers do like birds (Andy likes them, and Bob likes them). This is also known as [DeMorgan's Laws](https://en.wikipedia.org/wiki/De_Morgan%27s_laws), where "not both" is interpreted as "not(Andy likes birds and Bob likes birds)". DeMorgan's Laws say that this is logically equivalent to "(Andy doesn't like birds) or (Bob doesn't like birds)". Remember that this last "or" includes the intersection (the "middle" in a typical two-bubble Venn diagram---that is, the case where Andy doesn't like birds and also Bob doesn't like birds). The intersection ("and") is always included in the union ("or"). Imagine someone asked a room full of people, "stand up if you've got brown shoes or blue socks"---you'd stand up if you had brown shoes and any color socks, you'd stand up if you had blue socks and any color shoes, and you'd also stand up if your shoes were brown *and* your socks were blue. This is what your textbook authors are missing. Like many of the people who've posted here, I would never use the sentence "Both my brothers don't like birds," specifically because of the ambiguity. Most people don't know or care about set theory or mathematical logic, though some of them do, and even some of those who care don't know it well enough to interpret you correctly (e.g., your book's authors evidently knew DeMorgan, but forgot that the union includes the intersection). And even then, those who know and care about the set theory & logic might second-guess themselves, thinking *you* might not know it, or that you wouldn't expect *them* to know it, so... who knows what you meant?! Instead, I'd just say it more explicitly: one of the two bullet points above---either "Neither of them likes birds" or "One of them likes birds, but the other doesn't".

Not only is the textbook wrong but "Both my brothers" is also wrong, you would say "both of my brothers"

I mean… yes, TECHNICALLY, “both my brothers don’t like birds” could mean “it is not true that both my brothers like birds”. But it’s a very very confusing way to say that. And it’s still vague, as that statement is true whether 0 or 1 of your male siblings like birds. Most English speakers are going to assume the “both my brothers dislike birds” meaning. Like other commenters said, “neither of my brothers like birds” would be clearer and avoids the double negative. If one of them dislikes birds it would be better to positively state that, “one of my brothers dislikes birds” or “only one of my brothers likes birds”.

Should be: "Neither of my brothers like birds," or "both of my brothers dislike birds." And it absolutely does not mean that one does and the other doesn't. I can't think of any examples where "both" should be used in a negative sentence.

I suggest finding a new book! This one is incorrect and teaching you nonsense.

My thoughts are “My brothers both don’t like birds” = “Neither of my brothers likes birds.” “My brothers don’t both like birds” = “One of my brothers likes birds, and the other doesn’t,” because if neither of them did, I would have said it the first way. My brothers both {don’t like birds}. My brothers don’t {both like birds}. Edited to add: the sentence “Both my brothers don’t like birds” absolutely means the first—neither one of them likes birds. But if you wanted to communicate the second meaning, that’s how I’d do it.

The point of "'both' cannot be used in a negative sentence and 'neither' should be used instead" is formally correct. If you're doing a TOEFL or TOEIC test or college level writing, follow that rule. Otherwise, native speakers use "both" in that context so often that it doesn't really sound strange. At least in the US. In the commonwealth, it might be different.

You could say, 'both of my brothers have opinions on birds; one likes them and the other hates them'

I don't know Chinese so I can't comment on the translation, but "Both my brothers don't like birds" is poorly worded and sounds strange. Normally we would just say, "Neither of my brothers likes birds." If you were to say "Both of my brothers don't like birds", then its meaning is ambiguous. I think most people would think you are saying that neither one of your brothers likes birds, i.e. `¬P ∧ ¬Q`. However, that same sentence could also be understood (or perhaps misunderstood) to mean "It is not the case that both of my brothers like birds", i.e. `¬(P ∧ Q)` .

You are correct. Both (of) my brothers don't like birds = Neither of my brothers like birds = Both of my brothers dislike birds Also, 'both' can absolutely be used in a negative sentence - both you and I don't trust your textbook, for example.

Seems like some editors are sticking on outdated grammar books from 100 years ago

lots of posts in the sub lately featuring incorrect english information 😅

There’s probably some obscure rule that says that you can’t say both in a negative sentence but in practice that’s wrong. Your interpretation is correct of the sentence. They both don’t like.