In kana, a small
tsu (), called
sokuon, is used to indicate that the following consonant is
geminate, and in
interjections as a
glottal stop. In katakana only, a long vowel is indicated with a horizontal stroke () called a
chōon. This also looks like a half dash in braille: The placement of these blocks mirrors the equivalent kana: the
sokuon indicates that the following consonant is geminate, whereas the
chōon indicates that the preceding vowel is long. In kana, the
voiced consonants
g, z, d, b are derived from the voiceless consonants
k, s, t, h by adding a
diacritic called
dakuten to the kana, as in
gi; in foreign words,
vu is written by adding this to the vowel
u. Similarly,
p is derived from
h by adding a small circle,
handakuten. Two kana are fused into a single syllable by writing the second small, as in
kya from
ki + ya; this is called
yōon. In Japanese Braille, the signs for these are prefixes. That is, the order is
dakuten +
ki for
gi. When more than one occurs in a single syllable, they are combined in a single prefix block, as the
yōon-dakuten used for
gya. The
yōon prefix uses the dot that represents
y in the blocks
ya,
yu,
yo. When placed before
ka,
ku,
ko, it produces
kya,
kyu,
kyo. Likewise, the
yōon-dakuten prefix before
ka, ku, ko creates
gya, gyu, gyo. And so on for the other consonants. Unlike kana, which uses a subscript
e, in braille the
-ye in foreign borrowings is written with
yōon and the kana from the
e row: that is,
kye,
she,
che,
nye,
hye,
mye,
rye, voiced
gye,
je,
bye, and plosive
pye are written with the
yōon prefixes plus
ke,
se,
te,
ne,
he,
me,
re. The syllable
ye is written
yōon plus
e. There is also a prefix for medial
-w- called
gōyōon. When combined with
ka, it produces the obsolete syllable
kwa. It may also be fused with the voicing prefix for
gwa. For foreign borrowings, this extends to
kwi,
kwe,
kwo and
gwa,
gwi,
gwe,
gwo.
Gōyōon may also be combined with the vowels
i,
e,
o for foreign
wi,
we,
wo (now that the
w in the original Japanese kana for
wi,
we,
wo is silent); with
ha,
hi,
he,
ho for
fa,
fi,
fe,
fo and (when voiced) for
va,
vi,
ve,
vo; and with
ta,
chi,
te,
to for
tsa,
tsi,
tse,
tso. These two prefixes are identical to the question mark and full stop. These all parallel usage in kana. However, there are additional conventions which are unique to braille.
Yōon and
yōon-dakuten are also added to
chi and
shi to write
ti,
di and
si,
zi found in foreign borrowings; similarly
gōyōon and
gōyōon-dakuten are added to
tsu to write
tu,
du. This differs from the system used in kana, where the base syllables are
te and
to respectively, and a subscript vowel
i or
u is added. In an assignment that is counter-intuitive in kana,
yōon + handakuten is prefixed to
tsu,
yu,
yo to produce
tyu,
fyu,
fyo in foreign words, and voiced for
dyu,
vyu,
vyo. The latter—
yōon + dakuten + handakuten, is impossible in kana: ==Orthography==