Gairaigo

Gairaigo (kanji: Wai Lai Yu , hiragana: gairaigo) are loanwords in the Japanese language from languages other than Old or Middle Chinese. The word itself literally means "loan word". Most gairaigo come from European languages, and especially English since the post-WWII era, though Modern Chinese and Modern Korean are also popular sources for loanwords. Most gairaigo nowadays are written in katakana, with some older ones being written in ateji (kanji used only to show a word's pronunciation and not its meaning) or even in hiragana. For example, while America, or Amerika in Japanese, can be written as Ya Mi Li Jia in ateji, it is rare to do so these days, and instead it is almost always written in katakana as amerika.
Gairaigo is one of the three main sources of Japanese words, along with kango (kanji: Han Yu , hiragana: kango), or Chinese loanwords, and yamato kotoba (kanji: Da He Yan Xie , hiragana: yamatokotoba), or native Japanese words.
Gairaigo history
Japanese has a long history of borrowing words from other languages. Since the Chinese character system gave Japanese a writing system (as Japanese had no known systems of writing beforehand), the Japanese naturally borrowed many Chinese words into their language. However, the Japanese only borrowed words from other Asian languages until the Portuguese and the Dutch came to Japan during the 16th century. Since the Portuguese and the Dutch traded many different goods with the Japanese at this time, the Japanese naturally included many Portuguese and Dutch words into their own language, including karuta (ateji: Jia Liu Duo or Ge Liu Duo , hiragana: karuta, katakana: karuta) from the Portuguese carta meaning "letter", tempura (ateji: Tian Fu Luo or Tian Fu Luo , ateji and hiragana [most common form]: Tian pura, hiragana: tenpura, katakana: tenpura), from the Portuguese tempora meaning "temperance", as Catholics would not eat red meat during Lent, and tabako (kanji: Yan Cao , hiragana: tabako, katakana: tabako) from the Portuguese tabaco meaning "tobacco". While these terms used to be written mostly in ateji (and they still can be), they are now mostly written only in hiragana or katakana.
During the Meiji Period, after Matthew Perry forced Japan to open trade with other countries, Japan sent many scholars to Western countries to study different field of knowledge, such as Western medicine in Germany, an art in France. However, since the end of the 19th century, and especially after WWII, most gairaigo came from English. Today, about 90% of all gairaigo come from English.
Japanese-invented English words
While many gairaigo came from English, Japanese has also invented many new words based off of English, but wouldn't be understood by native English speakers. These are called wasei eigo, or "Japanese-made English words". Many of them are shortenings of English words such as amefuto (katakana:amehuto) which is a shortening of "American football", pasokon (katakana:pasokon) which is a shortening of "personal computer", konbini (katakana:konbini) which is a shortening of "convenience store", and anime (katakana: anime) which is a shortening of "animation". While each of these words have a longer gairaigo word that go along with them which would be amerikanfutoboru (katakana:amerikanhutsutoboru), pasonarukonpyuta (katakana:pasonarukonpiyuta), konbiniensusutoa (katakana:konbiniensusutoa), and animeshon (katakana:animeshiyon) in that order, they would be too long for a Japanese person to say in conversation. Also, some words got a new meaning when they come into Japanese. For example, "consent", or konsento (katakana:konsento) in Japanese, means "electrical outlet" rather than its original meaning, and "range", or (katakana:renzi) in Japanese, means "stove" rather than its original meaning.