Modern Chinese loanwords are generally considered gairaigo and written in katakana, or sometimes written in kanji (either with the more familiar word as a base text gloss and the intended katakana as furigana or vice versa); pronunciation of modern Chinese loanwords generally differs from the corresponding usual pronunciation of the characters in Japanese.
The first period of borrowing occurred during the late fourth century AD, when a massive number of Chinese characters were adopted.
This period could be considered one of the most significant in the history of gairaigo, because it was the first moment when the written communication systems using kanji were formed.
The first non-Asian countries to have extensive contact with Japan were Portugal and the Netherlands in the 16th and 17th centuries, and Japanese has several loanwords from Portuguese and Dutch, many of which are still used.
An example of the loanwords from Portuguese is rasha, meaning a thick wool cloth that was indispensable during the period, but not used often nowadays.
A more technical example is sorubitōru (ソルビトール) (English sorbitol) versus sorubitto (ソルビット) (German Sorbit), used synonymously.
In addition to borrowings, which adopted both meaning and pronunciation, Japanese also has an extensive set of new words that are crafted using existing Chinese morphemes to express a foreign term.
Due to Japanese pronunciation rules and its mora-based phonology, many words take a significant amount of time to pronounce.
For example, a one-syllable word in a language such as English (brake) often becomes several syllables when pronounced in Japanese (in this case, burēki (ブレーキ), which amounts to four moras).
For example, "remote control", when transcribed in Japanese, becomes rimōto kontorōru (リモートコントロール), but this has then been simplified to rimokon (リモコン).
For another example, the transcribed word for "department store" is depātomento sutoa (デパートメントストア) but has since been shortened to depāto (デパート).
Japanese ordinarily takes the first part of a foreign word, but in some cases the second syllable is used instead; notable examples from English include hōmu (ホーム, from "(train station) plat-form") and nerushatsu (ネルシャツ, "flan-nel shirt").
Similarly, gairaigo, while making Japanese easier to learn for foreign students in some cases, can also cause problems due to independent semantic progression.
As an example, left over is a baseball term for a hit that goes over the left-fielder's head rather than uneaten food saved for a later meal.
Infamously, the beverage brand Calpis sold a product named mai pisu or 'my piss' for a short time.
Some exceptions exist, such as sabo-ru (サボる, "cut class", from sabotage), which conjugates as a normal Japanese verb – note the unusual use of katakana (サボ) followed by hiragana (る).
Gairaigo function as do morphemes from other sources, and, in addition to wasei eigo (words or phrases from combining gairaigo), gairaigo can combine with morphemes of Japanese or Chinese origin in words and phrases, as in jibīru (地ビール, local beer) (compare jizake (地酒, local sake)), yūzāmei (ユーザー名, user name) (compare shimei (氏名, full name)) or seiseki-appu (成績アップ, improve (your) grade).
In set phrases, there is sometimes a preference to use all gairaigo (in katakana) or all kango/wago (in kanji), as in マンスリーマンション (mansurii manshon, monthly apartment) versus 月極駐車場 (tsukigime chūshajō, monthly parking lot), but mixed phrases are common, and may be used interchangeably, as in テナント募集 (tenanto boshū) and 入居者募集 (nyūkyosha boshū), both meaning "looking for a tenant".
Similarly, Japanese traditionally does not have any /v/ phoneme, instead approximating it with /b/, but today /v/ (normally realized not as [v] but as bilabial [β]) is sometimes used in pronunciations: for example, "violin" can be pronounced either baiorin (バイオリン) or vaiorin (ヴァイオリン), with ヴァ (literally "voiced u"+"a") representing /va/.
One important exception, however, does occur due to the fact that Japanese typically borrows English words in a non-rhotic fashion.
If the Portuguese word had been borrowed, it would most likely have taken the form オブリガド (oburigado), or maybe ōrigado (due to historical afu and ofu collapsing to ō), and while it is even possible that it would be spelled with 有難 as ateji, it would regardless start with o rather than a, and the final o would have been short rather than long.
Some gairaigo words have been reborrowed into their original source languages, particularly in the jargon of fans of Japanese entertainment.