Japanese has a large inventory of sound symbolic or mimetic words, known in linguistics as ideophones. Sound symbolic words are found in written as well as spoken Japanese. Known popularly as onomatopoeia, these words are not just imitative of sounds but cover a much wider range of meanings; indeed, many sound-symbolic words in Japanese are for things that don't make any noise originally, most clearly demonstrated by shiinto (?), meaning "silently".
These divisions are not always drawn: sound-symbolism may be referred to generally as onomatopoeia (though strictly this refers to imitative sounds, phonomimes); phonomimes may not be distinguished as animate/inanimate, both being referred to as giseigo; and both phenomimes and psychomimes may be referred to as gitaigo.
In Japanese grammar, sound-symbolic words primarily function as adverbs, though they can also function as verbs (verbal adverbs) with the auxiliary verb suru (, "do"), often in the continuous/progressive form shiteiru (?, "doing"), and as adjectives (participle) with the perfective form of this verb shita (, "done"). Just like ideophones in many other languages, they are often introduced by a quotative complementizer to (?). Most sound symbolic words can be applied to only a handful of verbs or adjectives. In the examples below, the classified verb or adjective is placed in square brackets.
|jirojiro (to) [miru]
|[see] intently (= stare)|
|kirakira (to) [hikaru]
|giragira (to) [hikaru]
|doki doki [suru]
|with a throbbing heart|
|guzu guzu [suru]
|procrastinating or dawdling|
(suru not optional)
|shiin to [suru]
|[be (lit. do)] quiet|
(suru not optional)
|pinpin [shite iru]
|[be (lit. do)] lively|
(shite iru not optional)
yoboyobo ni [naru]
|[become] wobbly-legged (from age)|
Note that, unlike the other examples, doki doki is the onomatopoeic sound of two beats of a heart.
In their Dictionary of Basic Japanese Grammar, Seiichi Makino and Michio Tsutsui point out several other types of sound symbolism in Japanese, that relate phonemes and psychological states. For example, the nasal sound [n] gives a more personal and speaker-oriented impression than the velars [k] and [?]; this contrast can be easily noticed in pairs of synonyms such as node () and kara () which both mean because, but with the first being perceived as more subjective. This relationship can be correlated with phenomimes containing nasal and velar sounds: While phenomimes containing nasals give the feeling of tactuality and warmth, those containing velars tend to represent hardness, sharpness, and suddenness.
Similarly, i-type adjectives that contain the fricative in the group shi tend to represent human emotive states, such as in the words kanashii (, "sad"), sabishii (, "lonely"), ureshii (, "happy"), and tanoshii (, "enjoyable"). This too is correlated with those phenomimes and psychomimes containing the same fricative sound, for example shitoshito to furu (?, "to rain / snow quietly") and shun to suru (, "to be dispirited").
The use of the gemination can create a more emphatic or emotive version of a word, as in the following pairs of words: pitari / pittari ( / ?, "tightly"), yahari / yappari ( / ?, "as expected"), hanashi / ppanashi ( / , "leaving, having left [something] in a particular state"), and many others.