Translation:I want a glass of milk.
From what I can see after researching a bit, there is no differentiation in Chinese between cup and glass. I wonder how that plays out in a restaurant? Does the waiter have to use their own discretion as to what the customer wants or is it just pot luck what you get?
Since we have no explanations on such matters with Duolingo, I think it is fair that you could say cup or glass in answer to this question, but that's always where you get a nice big WRONG once again, which undermines confidence for no educative purpose whatsoever. Literally being marked wrong for not knowing because nothing is explained.
Since the character is made up of the radicals for tree 木 mù and not 不bù, then it adds no light on the matter at all, a cup or glass is 'not a tree' backwards or 'tree not'. Weird.
It would be great if Duolingo could add a little explanation here and there as other Chinese language courses do. I find all too often I'm dabbling in the dark here - guessing sometimes, but not really knowing. The penalty for not having anything explained is being marked wrong. Doesn't give you much chance does it?
The plant/animal source doesn't matter. The way the language is used matters. Usually in English "milk" means cow's milk, so I would agree that 牛奶 can just be translated as milk. But, in Chinese, you can use 豆奶 for soy milk, and 椰奶 for coconut milk. Just like in English, where "milk" can mean almond milk or soy milk or any of that other stuff. Simply by usage, "milk" means the nutritive liquid produced by female mammals' mammary glands to support their young, and it also means a substance produced by other means that is sold/used as a substitute for mammalian milk (soy milk, almond milk, rice milk, etc).
Alfie, I agree with you. I was responding to Dejo. I agree that there are many types of 奶 (mammalian and plant-based) and so "cow's milk" is a better translation in some circumstances. Still, at least in the US, just "milk" implies cow's milk, so that should be acceptable too.