Would I have 牛乳 or ミルク with my cereal?

Question

I've just found out that there's a couple of words for milk, and that they have slightly different meanings. Which one would I have with my Weetbix in a "viking style" breakfast in Niseko?

Based on the following links: JREF and Japan forum page 1 and Japan forum page 2 it seems that:

1. 牛乳 refers to cow's milk in particular, and the kanji for cow and milk appear in it.
2. ミルク is the gairaigo term. It's used for baby's formula, coffee, tea, desserts, powdered milk, or to mean "milk flavored".
3. According to Berlitz Earworms (not any of the links mentioned), the Japanese for milk tea is ... "milk tea". Presumably the concept is so foreign they don't even add vowels to it or use cha!
4. お乳 is baby-talk for breast milk, and is also used for breasts. (I'm not sure if it means the breasts of a nursing human mother, or can mean the breasts of any woman, or whether it used to be innocent baby-talk for a nursing mother's breasts and is now used in a vulgar sexual way for any woman's breasts)
5. おっぱい is another childish way of referring to breasts and breast milk - perhaps without it being used in a slangy sexual way?
6. [母乳]{ぼにゅう} means mother's milk, non-babyish and non-slang.

Would I be correct in concluding that apart from breast milk or unprocessed milk, 牛乳 is used for traditional forms of milk, and ミルク is used when modern technology is involved and/or the milk is being used in a way that's untraditional (akin to the second paragraph of this answer on "Why was ライス borrowed from English")?

If so, would I use ミルク as having cereal and milk isn't native to Japan?

(Warning: googling only for miluku chichi produced some NSFW results)

Answer 1

I can get into this answer a bit because I'm lactose intolerant, or as it is called in Japanese, 乳糖{にゅうとう}不{ふ}耐症{たいしょう}.

Despite the fact that genetically, all Japanese should most likely also all be lactose intolerant, outside of medical practitioners, most people have never heard the term, and so usually it's easier to just say I have a milk allergy (牛乳{ぎゅうにゅう}アレルギー). There are complicated reasons for why Japanese can drink milk despite not having the lactase persistence gene, but this is a language forum, not a biology one. The point is that I come up against the Japanese perceptions and descriptions of milk products all the time.

For example, if I ask if a waiter if a dish has any milk products in it by asking about 乳製品{にゅうせいひん}, they are just as likely to say yes if it has another "milky" type thing in it, most notably soy milk: 豆乳{とうにゅう}. So I have to clarify that soy milk is okay, milk from cows (or other animals, though that's usually not an issue) is not.

So, finally getting around to your question more specifically, there is a concept of milk that predates western influence, bound in the kanji 乳{にゅう}. In modern usage, this can refer to mother's milk (母乳{ぼにゅう}), goat's milk (山羊{やぎ}乳{にゅう}), soy milk (豆乳{とうにゅう}), or any kind of milky product. Most usually there will be other kanji to differentiate.

The katakana ミルク almost always refers to cow's milk for drinking, following the American sense, and, as mentioned in comments, was a term brought over with widespread milk use in general after the war. However, I believe it more refers to the use than the source, because I have seen soy milk referred to as ソイミルク when it's for drinking (as opposed to cooking or making tofu). And, as you have seen, in other drinking contexts like ミルクティー.

In other words, saying ミルク instead of 牛乳{ぎゅうにゅう} doesn't do anything to clarify my problem any better, as they overlap too much.

In conclusion, in answer to your final question, you can have either ミルク or 牛乳{ぎゅうにゅう} with your cereal as you please. They have differences, but in that one particular context, both will be understood equally well.

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Lastly, on the issue of slang for breasts that you raise, 乳{にゅう} is used in contexts referring to breasts, such as 巨乳{きょにゅう}, "gigantic breasts", which you'll see all over men's (boy's?) magazines. The association between 乳{にゅう} and breasts is there, but like slang in general, it's flexible, so your experience might vary.

I've only ever heard おっぱい in reference to breasts, and I think it's on the same level as saying "boobs" in English. I don't doubt that it could also be a term for breast milk, just that maybe I don't hang around enough breast feeding children and their parents to have heard the term used that way.

Answer 2

In terms of the “substances” they could refer to, ミルク includes 牛乳, plus all the other examples that are given, like baby formula, creamer, and even semen (when used as sexual innuendo).

To keep it simple, let’s just say the “substance” we want to refer to is 牛乳. As long as it is clear in the context that you mean 牛乳, it isn’t technically wrong to use ミルク in place of the word 牛乳. (This also means than when it may be unclear what you are referring to, like when you want to ask where the milk aisle is at a grocery store, you should just say 牛乳.)

Still, even when it is perfectly clear, there are a few guidelines when choosing the less awkward term:

• In the list of ingredients in a written recipe, you would never use ミルク. (See the recipes at Cookpad. Even when the title contains the word ミルク, the ingredient is almost always listed as 牛乳.)
• The word choice normally defaults to 牛乳. Choosing ミルク is more deliberate, to sound perhaps more fancier/appetizing, or to blend in with the other words surrounding it (e.g. ホットミルク, ミルクスープ)

So to go back to the original question, A. シリアルに牛乳をかける / B. シリアルにミルクをかける are both correct and un-awkward, because the substance in question is unambiguous, A is the default, and in B, the katakana word シリアル is enough to justify the deliberate use of ミルク.