Let's take the は ひ ふ へ ほ (ha hi hu/fu he ho) kana for example. When they get
dakuten, they become ば び ぶ べ ぼ (ba bi bu be bo). The た ち つ て と (ta chi tsu te
to) kana become だ ぢ づ で ど (da dji dzu de do).

Why this transformation happens. And, more important, why the ち (chi) & つ
(tsu) are like this? They could have been ti, not chi and tu, not tsu. The ち &
つ kana could also be categorized in the わ & ん category. If they were ti and
tu, they could easily become di and du with dakuten.

So why does this happen? Why aren't they ti and tu instead of chi and tsu?
CC BY-SA 3.0
2017-07-24T13:48:25.587
51705
2017-07-24T17:49:10.250
question
kana kana-usage
た ち つ て と -> だ ぢ づ で ど (ta chi tsu te to -> da dji dzu de do) - Why is it different from all the other kana that can get dakuten?
The (surprisingly) short answer is: In Japanese, the かな are not out of line.
The **romanizations** that approximate these sounds as 'chi', 'tsu', 'dji',
'dzu', **are the ones out of line** , by virtue of the sounds not existing as
an easily approximated two-letter consonant-vowel pair.

> ta = た da = だ  
>  ti = ち di = ぢ  
>  tu = つ du = づ  
>  te = て de = で  
>  to = と do = ど

Basically, you really ought to be asking the question the OTHER way around:
Why are ち ぢ つ づ romanized as 'chi' 'dji' 'tsu' 'dzu'? And in thinking about
why that's the case, you'll have your answer. The order of かな actually makes a
lot of sense in the 五十音{ごじゅうおん} order.
CC BY-SA 3.0
2017-07-24T17:49:10.250
51711
2017-07-24T17:49:10.250
21684
51705
answer