How to choose between "よん" (yon) vs "し" (shi) for "四" (4) and "しち" (shichi) vs "なな" (nana) for "七" (7)?


Two numbers in Japanese have two pronunciation alternatives.

  * 四 / 4 can be pronounced either "よん" (yon) or "し" (shi)
  * 七 / 7 can be pronounced either "しち" (shichi) or "なな" (nana)

I know that "し" (shi) can be avoided because it has the same pronunciation as
"死" which means "death" but how strong is the taboo and how does it relate to
factors such as formality and politeness when choosing which form to use? Is
it just a matter of superstition or should speakers be more sensitive?

"しち" (shichi) vs "なな" (nana) seems to be less discussed since it doesn't
involve taboo or superstition as far as I know but again what about formality
and politeness etc?




よん is a 訓読み(kunyomi) reading of 4 and し is a 音読み(onyomi). なな is a kunyomi
reading of 7 and しち is a onyomi.

To make a long story short kunyomi is a native Japanese pronunciation and
onyomi are pronunciation that were derived from classical Chinese.

In the case of numbers shi and shichi (onyomi) is used when you are counting
things. For example, ichi ni san shi go, ... It is also used in months, like
四月(shigatsu) and 七月(shichigatsu)

When you point out that you have 70 yen you say nana juu en. (In this case use
kunyomi) Kunyomi is typically used in cases where you point out you have X of
some item. Counting in kunyomi is very unnatural so you almost never hear
people say ichi ni san yon go, ... but it is used when you count backwards.

These are just basic rules, there is one exception I can think of and that is
people, sometimes you do hear 七人(shichi-nin) when you talk about people.
However, as far as I know, it is very unnatural for people to use shi and
shichi used when talking about large numbers in the 10's, 100's, etc so use
the kunyomi (yon and nana) for that.




よん is a 訓読み(kunyomi) reading of 4 and し is a 音読み(onyomi). なな is a kunyomi
reading of 7 and しち is a onyomi.

To make a long story short kunyomi is a native Japanese pronunciation and
onyomi are pronunciation that were derived from classical Chinese.

In the case of numbers shi and shichi (onyomi) is used when you are counting
things. For example, ichi ni san shi go, ... It is also used in months, like
四月(shigatsu) and 七月(shichigatsu)

When you point out that you have 70 yen you say nana juu en. (In this case use
kunyomi) Kunyomi is typically used in cases where you point out you have X of
some item. Counting in kunyomi is very unnatural so you almost never hear
people say ichi ni san yon go, ... but it is used when you count backwards.

These are just basic rules, there is one exception I can think of and that is
people, sometimes you do hear 七人(shichi-nin) when you talk about people.
However, as far as I know, it is very unnatural for people to use shi and
shichi used when talking about large numbers in the 10's, 100's, etc so use
the kunyomi (yon and nana) for that.

