Japanese is the de facto official language of Japan, and Japan is the only country to have Japanese as an official working language. There are two forms of the language considered standard: hyōjungo (標準語, hyōjungo) or standard Japanese, and kyōtsūgo (共通語, kyōtsūgo) or the common language. As government policy has modernized Japanese, many of the distinctions between the two have blurred. Hyōjungo is taught in schools and used on television and in official communications, and is the version of Japanese discussed in this article.

Standard Japanese can also be divided into bungo (文語, bungo) or "literary language," and kōgo (口語, kōgo) or "oral language," which have different rules of grammar and some variance in vocabulary. Bungo was the main method of writing Japanese until the late 1940s, and still has relevance for historians, literary scholars, and lawyers (many Japanese laws that survived World War II are still written in bungo, although there are ongoing efforts to modernize their language). Kōgo is the predominant method of speaking and writing Japanese today, although bungo grammar and vocabulary occasionally appears in modern Japanese for poetic effect.