Two questions about numbers
Is there a contextual reason to choose between 'ku' and 'kyu' for pronouncing nine?
On my browser the kanji for eight looks like the katakana 'ha' but on my phone app has a little leg on the right hand stroke. Why is this?
Regarding the kanji for 8, that is likely just a difference in font or style. Same symbol, just written slightly different, with more pronounced 'ink trails".
As for 9, that is a bit more complicated. It does depend on context. In fact, depending on what is being counted, you can even end up prouncing Nine as "kokono". The most common reading is "kyuu", but it will vary depending on usage.
Here is an excerpt from an article discussing counting in Japanese that explains it better. The full article can be found here: http://www.japaneseprofessor.com/lessons/beginning/counting-in-japanese/
" Kanji Hiragana Romaji 1 一 いち ichi 2 二 に ni 3 三 さん san 4 四 し・よん shi/yon 5 五 ご go 6 六 ろく roku 7 七 しち・なな shichi/nana 8 八 はち hachi 9 九 きゅう・く kyuu/ku 10 十 じゅう juu
As you’ll notice, 4, 7, and 9 each have two pronunciations. In each case, the first pronunciation given is the on-yomi, or Chinese-derived pronunciation of the number. For 4 and 7, the pronunciations yon and nana both come from Old Japanese, rather than Chinese. Both kyuu and ku, however, are Chinese-derived readings.
But why have multiple pronunciations at all? Part of the reason is superstition – shi also means “death” and ku means “suffering”. Japanese people avoid 4 and 9 much the same way westerners are paranoid of the number 13, perhaps more so. The problem with shichi is less clear. I’ve heard it to be a reading of a Kanji meaning “hostage”, and also found one instance of it meaning “the proper place to die”.
Anyway, when simply counting, you really can use either pronunciation. But when counting something, like hours or people, either pronunciation for 4/7/9 might be the right one, and it’s difficult, though not impossible, to predict which.
Here are the two most common patterns:
Most Objects Less Common
1 ichi ichi
2 ni ni
3 san san
4 shi yon yo 5 go go
6 roku roku
7 shichi nana
8 hachi hachi
9 kyuu kyuu ku 10 juu juu
*Marks an “irregular” pronunciation compared to the normal on-yomi
Japanese people seem to use yon and nana most of the time, and kyuu is far more common than ku. You’ll also occasionally encounter yo for 4, really just a contraction for yon.
Note, however, that you cannot enumerate objects with Japanese numbers as is – you must add the appropriate counter."