In modern Japanese,  principally refers to kanji used to phonetically represent native or borrowed words with less regard to the underlying meaning of the characters. This is similar to  in Old Japanese. Conversely,  also refers to kanji used semantically without regard to the readings.

For example, the word "sushi" is often written with its  . Though the two characters have the readings  and  respectively, the character  means "one's natural life span" and  means "to administer", neither of which has anything to do with the food.  as a means of representing loanwords has been largely superseded in modern Japanese by the use of  (see also Transcription into Japanese), although many  coined in earlier eras still linger on.

Usage 
 today are used conventionally for certain words, such as  ('sushi'), though these words may be written in hiragana (especially for native words), or katakana (especially for borrowed words), with preference depending on the particular word, context, and choice of the writer.  are particularly common on traditional store signs and menus. For example, "tempura" may be written as . The Japanese loanword for "coffee" is generally written using the katakana , but on coffee shop signs and menus it may be written with the Chinese word , which is then pronounced irregularly to their normal Japanese reading (their ).

Many characters have gained meanings derived from  usage. For example,  were once widely utilized for foreign place names; such as in the   used to write "Asia". The original  word is now considered archaic, but the character  has gained the meaning "Asia" in such compounds as , even though  originally meant "sub-par" (and continues to). From the  , the second character was taken, resulting in the semi-formal coinage , which literally translates to "rice country" but means "United States of America"; however,  remains in far more common use in modern Japanese. Major natural gas companies in Japan use the   in their company names, but use the katakana  in their trade names.

Phono-semantic matching 

When using  to represent loanwords, the kanji are sometimes chosen for both their semantic and phonetic values, a form of phono-semantic matching. A stock example is  () for "club", where the characters can be interpreted loosely in sequence as "together", "fun" and "place". Another example is  () for the Portuguese , a kind of raincoat. The characters can mean "wings coming together", as the pointed  resembles a bird with wings folded together.

History 
The ad hoc usage of Chinese characters for their phonetic values dates nearly to the introduction of Chinese characters to Japan. Two widespread uses of  came out of this. On one front, scholars and monks used kanji characters as translation aids between the lines of Chinese texts. On the other, poets simply used kanji phonetically to write in Japanese. Many different characters were used with the same sound values.
This system of characters is called , "alphabet of myriad leaves". The  of modern Japanese,  and  developed as organic simplifications of  that were eventually codified.

 are primarily used today for historical terms – in historical order, these are primarily Sanskrit terms dating from the introduction of Buddhism to Japan, Portuguese terms from the 16th and 17th centuries, and Dutch terms from the 17th, 18th, and 19th centuries.  found some use in the Meiji period and in the 20th century, but has largely been superseded by .

Sanskrit 
In Buddhist Japanese, Sanskrit terms used in some chants also derive from  but were not called such. These Buddhist texts were translated into Chinese (in a Literary Chinese style) in China long ago. The translation rule for mantras was not to translate the mantra, but instead to represent it phonetically with Chinese characters. For the sutras, they were translated into Chinese Literary Language (). The terms  () and  (), or "perfection of wisdom" and "fully enlightened", both appear in the Heart Sutra, but are written using .

Related concepts 
 ("Japanese-origin" readings) should not be confused with . Whereas  are characters used to represent Japanese or borrowed words without regard to the meaning of those characters,  are readings, typically words, of Japanese origin that have been officially applied to the borrowed Chinese characters, similar to Latin-Germanic origin synonyms in English.

When a native Japanese word is written as a compound by meaning only, and this spelling is established in the language, as in , the word is the semantic variety of , and is known specifically as .

Intentional improvised use of irregular kanji spellings (as opposed to spelling mistakes) are known as , and generally require  (notational reading characters) to be read properly. Many  may have started out as . A loanword example is reading  as the English-derived word , or "rival".

While standardized  use , as in  having the suffix  in order to inflect as  for the past tense,  only intended for one-off usage need not have sufficient . For example,  ("spicy, salty") is an adjective requiring the suffix , but may also be spelt as, for example,  (both legitimate  of the characters) on a poster, for example, where there is no intention of inflecting this spelling.

Single-character loan words 
Most  are multi-character, but in rare cases they can be single-character, as in  (simplification of , for which  is the Chinese-derived pronunciation), used for "can, metal tin" ( originally meaning "metal pot, iron teakettle"). This is classified as .

In some rare cases, an individual kanji has a loan word reading – that is, a character is given a new reading by borrowing a foreign word – though most often these words are written in . The three most notable examples are , , and .  (from the Portuguese , "button") and  are marginally understood or used in some settings, but most are obscure – see list of single character loan words for more.

These are classed as  of a single character, because the character is being used for meaning only (without the Chinese pronunciation), rather than as , which is the classification used when a loanword term is using existing sounds only (as in  "tempura"), or alternatively as a compound with meaning only (as in  – the sound   cannot be broken down into readings of individual characters). In principle these could be considered as 1-character meaning-only , but because the reading corresponds to a single character, these are considered readings instead. Note that while  are generally written as  when writing out the word in  instead of kanji (because native Japanese), these  are generally written as  (because a foreign borrowing). See single character gairaigo for further discussion.

Note that numerically, most of these characters are for units, particularly SI units, in many cases using new characters () coined during the Meiji period, such as  from  "meter" +  "thousand"; this character is obscure and not in common use.

Some non-kanji symbols or Latin character abbreviations also have loanword readings, often quite long. A common example is '%' (the percent sign), which has the five kana reading  (), while the word "centimeter" is generally written as  (with two half-width characters, so occupying one space) and has the seven kana reading  (). It can also be written as , as with kilometer above, though this is very rare. Many borrowed measurement terms may be written as tiny abbreviations stuffed into a single character space called :  (for centimeters; ),  (for kilo; ), amongst others.

In a few cases, the etymology of a word is unclear, and hence whether the term is a borrowing or not cannot be determined.

There are occasional spellings which derive from  (Japanese form of literary Chinese), where the kanji form follows literary Chinese, but the pronunciation follows Japanese. An example of this is writing  (, "no, not") before a kanji for a verb, corresponding to the verb inflection  () – for example, writing  for   "not knowing". The word  is read as  (as if it were a native Japanese verb), though in this case  is also a Sino-Japanese word (a noun), read as , meaning "ignorance". These are primarily found in older literature, but are occasionally used in variant spellings of everyday words, such as .

See also

Japanese exonyms
 in Chinese
Transcription into Chinese characters

References

Further reading
 Painting Worlds and Words by Mia Lewis

Japanese words and phrases
Japanese writing system terms
Kanji
Transliteration