There are essentially three kinds of counters. One kind is used with Sino-Japanese series numbers. One kind is used with native series numbers. The other is used with a mixture of both.
Counters with 漢語系列の数詞
The overwhelming majority of counters of Sino-Japanese origin, as you would expect, are used with these numbers. This includes the large number units as they are counters as well. Some native counters are also used with these numbers such as 羽 (birds/rabbits), 割 (10%), 組 (school class), 型 (type), though 羽 is rather exceptional.
Recapping on Sound Changes
The following chart will help us remember what usually happens in regards to sound change for counter phrases.
|/k~/ 「回」||/s~/ 「冊」||/~t/ 「丁」||/h/ 「泊」||/other/ 「枚」|
Contraction Note: As we know, じゅう → じゅっ and じゅう → じっ are both correct, the latter is the traditionally correct form, but it is the former that is used the most today. It is to note that you must use じっ in set phrases such as 十把一絡げ (sweepingly), 十手 (short truncheon with a hook made of metal or wood used by policeman and private thief-takers in the 江戸時代), 十派（the ten sects of Rinzai Buddhism）, and 十傑 (ten biggest experts in a field).
For the most part, sound changes that occur with counter phrases can be summarized with the chart above. Understandably, when something is more technical such as 光年 (light year) or 海里 (nautical mile), a lot of people do not change いち → いっ. Additionally, there are more important things to addressed.
は行 Sound Problems
Most counters starting with a は行 change to p before ん. A small percentage of people don’t make a change at all. Some are restricted from changing with 4 such as 杯, 匹, 編, 歩, 方, and 本. Some counters like 杯 historically went to b in this condition, but it usually goes to p, though some speakers still change it to b or don’t change it at all.
票 is usually ぴょう, but some use びょう. Interestingly, when the number is high ひょう becomes more acceptable. Others such as 本 obligatory have a change of h to b excluding four. なんぽん is impossible. H to b generally lingers on in for most applicable numbers in the older population.
Other Voicing Before ん
足 gets voiced whenever it precedes an ん by the majority of people, although there are many who do not go by this sound change. なんぞく, in fact, is least common. 千 also does the same, giving us さんぜん and なんぜん. 羽 does too, but not so much with 4. So, we get さんば by some speakers.
階 and 軒 usually get voiced when preceded by ん but not with 4. さんがい and さんげん are both very common with their non-voiced counterparts used by quite a few people. なんがい is actually not used by the majority of people though it is traditionally the correct form, but なんけん and なんげん are equally used. In larger numbers, the likelihood of people voicing these counters drastically drops.
件 also rarely follows suit, allowing us to get 3件 read as さんげん.
促音化 of 6, 8, & 100
The rates of 促音化 for ろく and ひゃく in front of s and t is very low, although you may find this in use. For instance, hardly anyone says ろっとう. Most people say ひゃくとう but quite a few still say ひゃっとう. No one says ろっさつ. Oddly enough, some people do say ひゃっさつ. But, most people do say ひゃくさつ. Most people say ろっぽん and ひゃっぽん, but some people do use ろくほん and ひゃくほん.
8 often does not undergo sound change, but then it often does. For instance, most people say はっとう instead of はちとう. Essentially everyone says はっさつ, but people almost fifty-fifty either say はちかい or はっかい. Most people say はっぱつ, but some people are OK with はちはつ. The same goes for 8本. A considerable number of people say なんふん, though most say なんぷん. In fact, a small percentage of speakers don’t change 分 for 3 or 4.
羽 & 把
For 3羽 the majority of people say さんば, but many still sayさんわ. For 4羽, よんわ is used by most people. However, a few people say よんば and even fewer sayよんぱ. Those who say the latter are most likely misspeaking. As for 10羽, most people say じゅっぱ or じっぱ, but じゅうわ is used by a lot of people. 何羽 is usually なんわ. However, some say なんば and very few sayなんぱ. With 千 and 万, the readings are ば (a lot), わ (quite a few), ぱ (not many).
By analogy, 把 (bundles) is also affected. Though わ is always the most common reading, many say じっぱ・じゅっぱ, quite a few say さんば, and some do sayよんば, さんぱ, よんぱ.
Of course, 人 has the exceptional ひとり and ふたり, but those are actually read as いちにん and ににん respectively when used with前 to express portion sizes and other set phrases.
Time Phrase Exceptions
Time phrases are a mess when it comes to conformity. 年 takes よ for 4 but either きゅう or く for 9. Other things such as 年生 and 年度 behave the same.
We know how we should say しがつ, しちがつ, and くがつ for April, July, and September respectively.
Day becomes an even more confused mess. You know of ついたち, ふつか, みっか, よっか, いつか, むいか, なのか, ようか, ここのか, とおか, and the like. You also know that other days such as 17日（じゅうしちにち） have set readings. However, you probably don’t know that some speakers turn にち to んち when possible or that there are many who say じゅうななにち instead of じゅうしちにち. This is dialectical, but it’s important to know that it does exist. However, these speakers interestingly never use this contract with 千 or何.
As for 時 and 時間, よ and く must be used for 4 and 9 respectively. You can say しちじかん and ななじかん, but you can only say しちじ. Though not imperative, よ and く are used frequently with other counters that begin with じ.
There are also foreign counters that we can group with counters who take Sino-Japanese numbers. The majority of such counters are actually measurement words.
In principle, most foreign counters stay the same and don’t undergo a sound change although one would otherwise be possible. So, things like フィート and ヘルツ would never change.
It’s rare to hear something like じゅっフィート or the like, but the counter itself never changes. Even Sino-Japanese counters such as 平方 don’t change due to a great association with foreign word (Ex. 平方メートル).
For パーセント (percent), PPM, ページ (page), and ポンド (pound), 1, 8 and 10 frequently undergo sound change. よ and く are also not used with foreign counters. So, you won’t ever hear よメートル or くメートル. Others such as キロ, センチ, and トン behave like any other counter. So, you get things like いっキロ, ろくトン, and はっセンチ. Exceptionally, いちキロ happens to be more common than いっキロ.
Other normal counters include ㏄, カラット (carat), カロリー (calorie), キログラム (kilogram), グラム (gram), アール (are), アンペア (ampere), インチ (inch), オクターブ (octave), ダース (dozen)、 デシベル (decibel), ドル (dollar), ボルト (bolt), マイル (mile), マルク (marc), リットル (liter), メートル (meter), ヤード (yard), ルクス (lucs), ワット (watt), etc.
It’s important to note that though the percentages of sound changes to numbers are just as likely with these foreign counters, there are a few instances when it is less likely. For instance, if you have one starting with s such as シート, 1 typically does not undergo sound change and 8 doesn’t half of the time. The exact percentages of people using sound changes or not with foreign counters differ for each one, but most allow you to go with or without. However, 8キロ and 100キロ are always pronounced with 促音化, so there are even exceptions to this principle.
Using Native Numbers
As for counters that take Japanese numerals, we know of the important counters つ, か (日), つき (月), and り (人). Understand that つき is used to count 月数 but か is for both 日付 and 日数. Consider the following chart.
We see that とお and つ do not go together. We also know that か is not used with 1 and the expression is made with ついたち instead. The reading いっぴ may also be used in official documents. We also know that we can use Sino-Japanese numbers with にち if we count 日数. Though not in the chart, we also get はつか for #20. The pattern of using か with native numbers stretches from #2~10 and #20 but not in between. You can say じゅうよっか and にじゅうよっか, but you can view these as hybrid expressions. Children may say じゅうよ（ん）にち, but people largely do not. There is also みそか for #30 used primarily in 大晦日 (New Year’s Eve), but the pattern does not stretch in between 20 and 30. The expression いくか did exist, but it has since disappeared completely.
More exceptions abound. For example, にひゃくとおか means the 210th day from the first day of spring according to the lunar calendar. It marks what is supposed to be the start of typhoon season. Then there’s the 百八つの鐘 struck 108 times at midnight on New Year’s Eve to ward off omens and evil spirits.
The reason for why usage of つき beyond 4 is put in parentheses is because at this point is common practice to use ヶ月 instead. Using 1~4 with つき is most expected of people that are older. This is already more frequent for 1~4 as well. This is aside from set phrases such as 十月十日 meaning the average gestation period and 六月・睦月meaning the sixth month of the lunar calendar.
As for り, み（っ）たり, よ（っ）たり, いくたりhave existed and survive in isolated dialects, but they have otherwise dropped out of use entirely.
Other Limited Native Counters
Similar counters that take native numbers include 重, 言, 雫, 度, 年, and 夜. Excluding exceptions such as 八重桜 (double-flowered cherry tree), these counters are generally not used past 2 or 3, and most have limited usage. Some are frequently used such as ひとえ, ふたえ, みえ (primarily used as the name of a prefecture), or 再び (spelled differently), or ひとこと, but the rest are just not so common and typically used in specialized contexts.
Mix of Sino-Japanese and Native Numbers
Then there are the counters which are used with a mix of Sino-Japanese and native numbers. These counters are particularly the most confusing as they present the learner great disagreements among speakers as to which pronunciation is the most correct. Below is a list of counters that full under this category.
色, かご, カップ, 缶, 口, クラス, ケース, 桁, さじ, 皿, 試合, シーズン, 品, 種類, すじ, セット, 束, チーム, 粒, 坪, 箱, パック, 針, 晩, びん, 袋, 房, 部屋, 間, 棟, 目, 目盛り, 文字, 役, 切れ, 組, 揃い・揃え, 包み, 通り, 巻き.
What all of these counters have in common is that they either come from regular nouns or the 連用形 of verbs. To get a taste of what sort of options you have, consider the following chart with 箱 and 通り.
|箱 Boxes||通り Methods|
The trend is that if it is a very small number, then the native unit is most likely. Depending on the counter, whether a native unit can be used or not varies a lot. Even though something like みはこ may be possible, younger speakers don’t use it at all. Expressions like みびん and みケース don’t even exist. In fact, み itself has mostly disappeared in today’s generation aside from date phrases. Even though you can say いちしあい, you can’t say いちへや. Though ひとはこ and ふたはこ are by far the most common, みはこ and よはこ are far from it and いっぱこ and にはこ marginally exist. Some people even say さんばこ, さんぱこ, and よはこ. However, you never see something like さんべや. There is a lot of variation and gaps in generations as to what other tweaks you can make to these phrases.
Some of these words would just never get used beyond a certain number anyway, so in these cases it’s best not to think about the what if.
Below are some percentages for the readings of similar counters.
Phrases in bold are used by 70% or more of Japanese people. Phrases that are at least used by 20-45% of the population will be let as normal, and those that are used by less than 20% will be left in parentheses as questionable. Variants will be listed in order of most to least frequent.
*: にしん is essentially only used with 時計の二針, and it is ふたはり that is actually constructive. For instance, people say ふたはり縫う. People don't say にしん縫う.