Should it not be い かい as I thought the counter for floors was -kai ?
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2016-10-26T12:15:07.547
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2016-10-27T13:06:45.780
2016-10-26T13:57:06.970
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question
pronunciation counters numbers
Why is 1st floor written as ikkai いっかい?
Because of
[促音便](https://ja.wikipedia.org/wiki/%E9%9F%B3%E4%BE%BF#.E4.BF.83.E9.9F.B3.E4.BE.BF),
the pronunciations of いち, ろく, はち, じゅう, ひゃく change to いっ, ろっ, はっ, じゅっ/じっ, ひゃっ
when followed by some counters, like this:

> いち + かい → い **っ** かい (1回/1階)  
>  ろく + かい → ろ **っ** かい  
>  はち + かい → は **っ** かい  
>  じゅう + かい → じゅ **っ** かい  
>  ひゃく + かい → ひゃ **っ** かい
>
> いち + こ → い **っ** こ (1個)  
>  ろく + ひき → ろ **っ** ぴき (6匹)  
>  はち + ほん → は **っ** ぽん (8本）  
>  じゅう + ふん → じゅ **っ** ぷん/じ **っ** ぷん (10分)  
>  いち + てん → い **っ** てん (1点)  -- but 6点, 100点 are ろくてん, ひゃくてん  
>  はち + さい → は **っ** さい (8歳)  -- but 6歳, 100歳 are ろくさい, ひゃくさい

etc...
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2016-10-26T12:54:50.503
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2016-10-26T13:27:46.557
2016-10-26T13:27:46.557
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answer
It is a phonetic transformation similar in English to "aren't".  
Instead of saying "are not", you can say "aren't".  
Instead of saying "いちかい", you say "いっかい".  

The difference is that in Japanese the pronunciation is not optional. You have
to say いっかい. It is wrong to say いちかい.  
Most of these words are listed in dictionaries and in good grammar books.
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2016-10-27T13:06:45.780
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answer