What is independent form of numeral 10?

Question

An old Dover grammar-book of Japanese shows it to be to (it has no kana but I assume it's と), but Wikipedia shows to̅ (とお). Which one is correct?

Answer 1

It is 「とお」 as explained in the Q&A I linked to above. That is how "10" is read in the original Japanese way (prior to our dramatic encounter with the Chinese).

Listen to this video from 0:25 and you will see that it is the elongated 「とお」 and not the regular-length 「と」.

In actual words, however, the kanji 「十」 are read both ways. Which one to use depends on the word.

「とお」： 「十日{とおか}」 ("10th day of the month")

「と」： 「十度{とたび}」 ("10 times")

My Favorite: 「十月十日{とつきとおか}」

The first 「十」 is read 「と」 and the second, 「とお」. This is how we figuratively and rhythmically describe the normal length of human pregnancy before delivery -- "10 months and 10 days".

For the date "October 10th", however, 「十月十日」 is read 「じゅうがつとおか」. As far as pronunciation, the first 「十」 is Chinese-influenced, but the second 「十」 is originally Japanese.