Wo (kana)

を, in hiragana, or ヲ in katakana, is one of the Japanese kana, each of which represents one mora. Historically, both are phonemically /wo/, reflected in the Nihon-shiki wo, although the contemporary pronunciation is [o] ^ⓘ, reflected in the Hepburn romanization and Kunrei-shiki romanization^[1] o. Thus it is pronounced identically to the kana o. Despite this phonemic merger, the kana wo is sometimes regarded as a distinct phoneme from /o/, represented as /wo/, to account for historical pronunciation and for orthographic purposes.

In the 1946 orthographic reforms, を was largely replaced by お. In Japanese, this kana is used almost exclusively for a particle for both forms; therefore, the katakana form (ヲ) is rare in everyday language, mostly seen in all-katakana text. A "wo" sound is usually represented as うぉ or ウォ instead.

Despite originally representing [wo], the mora is pronounced [o] by almost all modern speakers. Singers may pronounce it with the [w], as a stylistic effect. Apart from some literate speakers who have revived [wo] as a spelling pronunciation, though, this [w] sound is extinct in the modern spoken language. Some non-standard dialectal Japanese still pronounce it [wo], notably dialects in the Ehime Prefecture.

In Romaji, the kana is transliterated variably as ⟨o⟩ or ⟨wo⟩, with the former being faithful to standard pronunciation, but the latter avoiding confusion with お and オ, and being in line with the structure of the gojūon. を is transliterated as o in Modified Hepburn and Kunrei and as wo in Traditional Hepburn and Nippon-shiki.

Katakana ヲ can sometimes be combined with a dakuten, ヺ, to represent a /vo/ sound in foreign words; however, most IMEs lack a convenient way to do this as this usage has largely fallen into disuse. The digraph ヴォ is used far more frequently to represent the /vo/ sound.

Hiragana を is still used in several Okinawan orthographies for the mora /o~wo/; in the Ryukyu University system, it is /o/, whereas お is /ʔo/. Katakana ヲ is used in Ainu for /wo/.

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