Japanese counters can seem very difficult at first. You can’t just say “two pencils”, “seven cats” or “ten sheets of paper” the way you can in most languages. You need to know the counter for long round things, small animals and thin flat things respectively.
Not only that, but the pronunciation of the counter changes depending on what number it is used with. The counter for small animals is called hiki but in fact:
1 cat is ippiki
2 cats are nihiki
3 cats are sanbiki
4 cats are yonhiki
5 cats are gohiki
6 cats are roppiki
7 cats are shichihiki or nanahiki
8 cats are happiki
9 cats are kyuuhiki
10 cats are juppiki
And then different counters have different patterns of sound-change.
How Counters’ Sound Patterns Transform
It looks crazy, but in fact it is a lot simpler than it seems. Once you learn how it works you will be able to figure out how nearly any counter sounds for any number.
Look at the sub-heading above and commit it to memory. Here, I’ll give it to you again:
How Counters’ Sound Patterns Transform
You need to remember this phrase. Why? Because actually there are only five types of transforming counter (only?… no don’t panic, I’m going to help you). They are counters that start with the consonantal sounds H, K, S, P and T. That is why you should remember that phrase – How Kounters’ Sound Patterns Transform.
Or, if it is easier, you can remember this way: it is the “hard”-consonant counters that transform, not the “soft”-consonant ones like mai, rin, wa and bu. This makes even more sense when you see how they work, since (with a single maverick exception) they always transform by sharpening or doubling the hard sound – you actually can’t double soft consonants in Japanese. You never see a small tsu before m, b, or w.
Now, once you know that, you will be pleased to learn that the transformations are very regular. What throws people, I think, is that single maverick we spoke of before. H-row sounds turn to the B-equivalent when paired with san (as in sanbiki)*. But actually that is the only major irregularity.
Other than that all the HKSPT counters modify in the same way. In a few cases the modification is optional, but you can always use it without fearing to make a mistake.
So, leaving out the H row for a moment, all the other mutating counters (K,S,P,T) follow the same pattern:
1. They all keep their base value for all numbers other than one, six, eight and ten (jump from one to six, then every alternate number).
2. As for those four numbers, they all do the same thing:
They simply drop the second syllable of the number and double the first consonant of the counter. So ni-ko and san-ko but ikko rather than ichi-ko and jukko rather than juu-ko.
The only regular exception to this is that the S and T counters don’t mutate for 6 (roku) – i.e. no ross- or rott-.
The H-row is really less puzzling than it seems too. It only changes to the sounds that are made with the H-row by adding diacritical marks so, in the case of ひき hiki, it becomes びき biki (for that maverick san only) and っぴき ppiki for the regular doubled-consonant numbers, one, six, eight and ten. Since you couldn’t actually have hhiki, that isn’t very hard to remember.
Now I won’t pretend there aren’t a few other irregularities with counters (hun, the counter for minutes, for example doesn’t get the b-mutation on 3, but is sanpun rather than sanbun). But this pattern will guide you through most of the ones you are going to use. Even Japanese people mostly don’t use the more obscure counters.
The important thing to realize is that it is a pattern that works nearly all the time, not just a set of confusing random sound-changes. And if the counter does not begin with H,K,S,P or T, it will not have sound-changes at all.
Remember that you don’t need counters if you use the native Japanese counting system – hitotsu, futatsu mittsu. However you should know and use the basic counters like hon, hiki, hai, mai, ko, etc
If you work through the explanation on this page (it sounds a bit more complicated in text than it really is), the pattern of the sound changes should fall into place for you and the whole thing will feel much more intuitive.
* There is a sound-logic to the san-b transformation too, but for our practical purpose here it is simpler just to think of it as a maverick.