Are units counters?
I'm confused about how to use measurements (like kilometres, gramme, etc.) in a japanese sentence.
As far as I understood it, those units are used as counters, which means that you can formulate sentences like:
砂糖を二百グラム買った。(I bought 200g of sugar.)
その建物は六メートルの高さだ/高さがある。(That building is 6m high.)
What confuses me however, is the way Duolingo uses measurements. There was for example this sentence この新幹線は一時間に三百キロ進みます。(This bullet train goes three hundred kilometres an hour.) I feel like there is a particle missing (and the noun the counter refers to)... Or else, what kind of word is "three hundred kilometres" in this sentence if you don't need a particle (and another noun)?
Thank you for your help!
Hi! You know how English counts uncountable things and groups of things? Like a loaf of bread, a glass of water and a school of fish? Japanese does the same, only it applies the same principle to all nouns, not just the uncountable. So in Japanese, you'd always have noun+particle+counter (and no particle, because the noun already has it.)
Some counters, though, have very narrow scope of use, like キロ. It’s either kg or km, and we measure only distance with km, just like when we say loaf in English, it’s practically always bread. So you say キロ and distance is understood, and you say loaf and bread is understood.
But Japanese is also very big on contracting parts of the sentence that are implied or understood. So you'd often drop the noun and leave the counter. Hence, the shinkansen goes forward (進む) by 300kms, and “of distance” is implied. When the counter is used for something less default, like height or depth, then that does not get dropped and you get the sentence about the building that “possesses” a height of six meters. Just like you can say in English “I bought a loaf” and bread is implied, but if you bought something else that comes in loaves, you need to say what.
The noun can also be dropped in context, and the counter will still stay particle-less, like in conversation:
Yamada: あ！田中さん、新しい車ですね！ Tanaka: 二台買いましたよ！
I hope this helps, but if it doesn’t, let me know and I'll try again. :)
It sounds like you're asking if there needs to be a noun or particle? Your options are to apply the measurement to a noun, another measurement, or a verb.
When used with a verb, particles aren't needed, just like an indicator isn't necessary in English. For example: I walked 15 kilometers. 十五キロ歩きました。So in the example you gave, the 三百キロ is modifying the 進みます, which means that the train goes 300 kilometers. No noun would make sense in this context. You can't travel 300 kilometers of trains. In a different context, like 肉を二百グラム買った a noun is necessary because the グラム is not modifying the 買った; you can't buy 200 grams times like a train can go 300 kilometers [distance], and likewise a train can't go 300 kilometers of train but you can buy 200 grams of meat.
So when the measurement is modifying a verb directly, nothing else is needed. Counters are usually used to modify nouns, which is why they tend to behave differently. A great example is noting how the 回 and 度 counters work in comparison to other counters.