日本語のおしゃべり Nihongo no Oshaberi

Japanese Orthography
(Part 3)

「Transliteration of foreign words, voiced, twisted, and assimilated sounds」

Transliteration
With the transliteration of foreign words into katakana, long vowels are denoted with the uses of a lengthening stroke (ー)

Examples:
コーヒー　　Kōhī　　Coffee
ビール　　Bīru　　Beer
ボール　　Bōru　　Ball(s)
エスカレーター　　Esukarētā　  Escalator

Two exceptions to this extension stroke rule are Eight (エイト) and Spain (スペイン)

”Voiced” Sounds
"Voiced" sounds (daku-on or "Muddied" sounds) g-, z-, d-, and b- are identified with usage of short diagonal strokes (nigori) on the upper right-hand corner of the unvoiced character, and the "half muddled" sound (hanadaki-on) p- is primarily denoted with a small circle (maru)

Examples:
Ga 「が・ガ」　Za「ざ・ザ」　Da「だ・ダ」　Ba「ば・バ」　Pa「ぱ・パ」

"Twisted" Sounds
"Twisted" sounds (Yō-on) also borrow characters from hiragana and katakana, they are denoted with two kana; the first being from the i column, and the second from the ya row. The smaller kana is used to denote the merging of the two separate characters into a single syllable.

Examples: 
Kya 「きゃ・キャ」　Kyu「きゅ・キュ」　Kyo「きょ・キョ」
Gya「ぎゃ・ギャ」　Gyu「ぎゅ・ギュ」　Gyo「ぎょ・ギョ」

”Assimilated” Sounds
”Assimilated” sounds (soku-on) otherwise known as sounds that are represented when using romaji by a doubled consonant , these are identified by a small つ・ツ before the extended consonant sound.

Examples:
れっしゃ　Ressha　　Train
　　じっぷん　　Jippun　　Ten Minutes
ロケット　　Roketto　　Rocket

ʿʿ˅⁽ˆ⁰ˆ˺ ⁾˺　こゆうきあいはら　ʿʿ˅⁽ˆ⁰ˆ˺ ⁾˺