How to read 4, 7, and 9 causes headaches for many learners. It’s easy to know that they are usually read as よん, なな, and きゅう respectively. Yet, although し, しち, and く are heavily restricted., they are still used. So, when are they used?
し, しち, and く are not used with larger number units in the initial position. These numbers in larger numbers are limited to set phrases such as 四百四病の外 (＝恋の病) and 九十九里. Exceptionally, in stating one’s age without a counter, using し (4) or しじゅう (40) is not wrong but highly unlikely. Although it is true that Sino-Japanese numbers are widely preferred in counter phrases, 4 and 7 are exceptional.
Consider 4枚 as a great example of reading trouble. Usually it is read as よんまい and never しまい, but the reading よまい and しまい exist in the set phrase 四枚肩 (a palanquin usually carried by two people being carried by four people). It may be read as either しまいがた or よまいがた. This example shows us that we must look at 4 on an individual basis.
Aside from the situations し is acceptable and or expected, there are many important phrases it obligatorily shows up in. As examples, consider 四角 (square), 四季 (the four seasons), 四国 (Shikoku), and 四天王 (the big four/the Four Heavenly Kings).
So, when you don’t use し, よん and よ are your next two options. よん is overwhelmingly used, and as we’ve seen よ is preferred particularly in set phrases such as 四段活用 (old name for 5段 verbs in Classical Japanese which had four vowels in the bases rather than five). Nevertheless, there are counters such as 人, 時, 時間, 度 (degrees) and 円 (yen) that require よ. Require, though, is not the best word as there are speakers who do say よんえん. Again, aside from set phrases, you don’t use し with counters.
Let’s consider more instances of various and not so various readings of 四.
40過ぎ is usually よんじゅうすぎ. However, the older population still use しじゅうすぎ at times. Of course, there are instances when し is not acceptable at all. For instance, in fractions no one says しぶんのいち for 1/4th. Instead, everyone says よんぶんのいち. Likewise, people always read 四割 (40%) as よんわり.
As generations go by, the usage of なな increases as the usage of しち decreases. For instance, 七時間 (7 hours) is read as ななじかん by most people, although there are still many people who use しちじかん. Though standardized to be read as じゅうしちにち, 十七日 (the 17th) is じゅうななにち for half of the country (West Japan). It’s also interesting to know that the majority of people use なな instead of しち in countdowns. This is in contrast to 4 as no particular reading is preferred in countdowns.
However as is the case with 4, the latter shows up in set phrases, making なな incorrect in those instances.
|七五三||Festival for children 3, 5, and 7|
|五七調||Five-and seven-syllable meter|
|七転八倒||Writhing in agony|
Reading Note: 七五三縄 is completely exceptional and is read as しめなわ。 This is a Shinto rope used to cordon off consecrated areas as a means of protection from evil forces.
く at one time was the most prevalent reading for 九. Now it is on the decline. For instance, きゅうにん is more common thanくにん. Also, there are now phrases such as 九割 (90%) in which only きゅう can only be used.
However, く does lag on in set expressions but also with particular counters such as 度. For instance, 39度 (39 degrees) is often pronounced as さんじゅうくど. Of course, there are also phrases such as 9月, 9時, and 9時間 in which you can only use く. Another example of obligatory く is 九分九厘 meaning that something has a 99% chance.