About two weeks after I finished learning katakana, I was looking at a menu at a Japanese restaurant and realized I could read it. Not translate it. I didn't know the kanji for most things. But the katakana section just... opened up. コーヒー. ケーキ. アイスクリーム. I knew all of those words. I just hadn't seen them written that way before.
That's the hidden reward of learning katakana. You've also been learning Japanese vocabulary for your entire life, just without knowing it. English words are all over Japanese: technology, food, fashion, sports, entertainment. And they're almost always written in katakana. Once you can read the script, a huge portion of the vocabulary is already yours.
The catch is that English words don't travel to Japanese unchanged. They get adapted to Japanese phonetics, and the result can be hard to recognize if you're not prepared for it. This guide covers the rules of that transformation, how Japanese reshapes English sounds, and what to do when you hit a word you can't quite place.
What gairaigo actually is
The Japanese term for borrowed foreign words is 外来語 (*gairaigo*), literally "words that came from outside." Japanese has been absorbing foreign vocabulary for centuries: first from Chinese (which gave the language kanji), then from Portuguese in the 16th century (bread as パン from *pão*, playing cards as トランプ from *trump*), then from Dutch, French, German, and eventually English on a massive scale.
Today, the vast majority of gairaigo in everyday Japanese comes from English. Estimates put the total number at somewhere between 30,000 and 60,000 words. These aren't obscure technical terms. They're in daily conversation, on menus, in advertising copy, in song lyrics, on packaging at every convenience store. You cannot read real Japanese without running into them constantly.
All of this gets written in katakana. That's katakana's primary job: marking the foreign.
The sound shift rules
Japanese and English have very different sound inventories, and when English words get borrowed into Japanese, they go through a process of phonetic adaptation. The word gets rebuilt using available Japanese sounds. Once you understand the main rules, you can start guessing at words you've never studied. You'll be right more often than you'd expect.
L becomes R
Japanese doesn't have an L sound. It has one liquid consonant, the R sound, which sounds something like a cross between English R, L, and D. Every English L becomes a Japanese R:
- level → レベル (*reberu*)
- lemon → レモン (*remon*)
- hotel → ホテル (*hoteru*)
- color → カラー (*karā*)
- alcohol → アルコール (*arukōru*)
This one trips people up a lot when they're listening to Japanese and trying to recognize words. Once you've internalized it, you start hearing it immediately.
Long vowels use ー
The long vowel mark ー (*chōonpu*) stretches the preceding vowel. It appears constantly in loanwords because English has a lot of long vowels and diphthongs that Japanese needs to approximate:
- coffee → コーヒー (*kōhī*)
- cake → ケーキ (*kēki*)
- beer → ビール (*bīru*)
- game → ゲーム (*gēmu*)
- door → ドア (*doa*) (no stretch here, since "door" ends in a short vowel sound)
When you see ー, just hold the previous vowel a beat longer. In everyday reading it becomes automatic fast.
Consonants that land differently
English has sounds that don't exist in Japanese, so substitutions happen:
V → B: Japanese has no V sound. Every English V becomes B.
- virus → ウイルス (*uirusu*)
- volume → ボリューム (*boryūmu*)
- video → ビデオ (*bideo*)
TH → S or Z: Japanese also has no TH. Voiced TH ("the", "this") usually becomes Z; unvoiced TH ("three", "thanks") becomes S:
- theme → テーマ (*tēma*) (actually from German *Thema*, pronounced with a T)
- marathon → マラソン (*marason*)
F → フ only: Japanese only has one F sound, フ (*fu*). So English F words have to rework their vowels:
- file → ファイル (*fairu*) (using the small ァ after フ)
- fan → ファン (*fan*)
- fork → フォーク (*fōku*)
- sofa → ソファ (*sofa*)
Final consonants get a vowel
Japanese syllables almost always end in a vowel (or N). When an English word ends in a consonant, Japanese typically adds a u sound, or sometimes o after a T or D:
- desk → デスク (*desuku*)
- risk → リスク (*risuku*)
- bed → ベッド (*beddo*)
- card → カード (*kādo*)
- test → テスト (*tesuto*)
- sport → スポーツ (*supōtsu*)
Double consonants become ッ
When English has a doubled consonant or a hard stop before another consonant, Japanese uses the small ッ (*sokuon*) to represent it:
- bed → ベッド (*beddo*) (the D doubles)
- better → ベター (*betā*) (sometimes the double is dropped)
- pocket → ポケット (*poketto*)
- ticket → チケット (*chiketto*)
- soccer → サッカー (*sakkā*)
Words you can read right now
With those rules in mind, here are categories where gairaigo dominates:
Food and drink
- コーヒー (*kōhī*): coffee
- ケーキ (*kēki*): cake
- ハンバーガー (*hanbāgā*): hamburger
- ピザ (*piza*): pizza
- サラダ (*sarada*): salad
- アイスクリーム (*aisukurīmu*): ice cream
- チョコレート (*chokorēto*): chocolate
- ジュース (*jūsu*): juice
- ビール (*bīru*): beer
- ワイン (*wain*): wine
- バター (*batā*): butter
- チーズ (*chīzu*): cheese
- パスタ (*pasuta*): pasta
Technology
- テレビ (*terebi*): TV
- スマホ (*sumaho*): smartphone (short for *sumāto fon*, smart phone)
- コンピューター (*konpyūtā*): computer
- インターネット (*intānetto*): internet
- カメラ (*kamera*): camera
- ゲーム (*gēmu*): game
- アプリ (*apuri*): app
- パソコン (*pasokon*): personal computer (another abbreviation)
- データ (*dēta*): data
- メール (*mēru*): email
Sports and hobbies
- サッカー (*sakkā*): soccer
- テニス (*tenisu*): tennis
- バスケットボール (*basukettobōru*): basketball
- ゴルフ (*gorufu*): golf
- スキー (*sukī*): skiing
- サーフィン (*sāfin*): surfing
- ジョギング (*jogingu*): jogging
Everyday life
- タクシー (*takushī*): taxi
- ホテル (*hoteru*): hotel
- マンション (*manshon*): apartment (not mansion, covered below)
- エレベーター (*erebētā*): elevator
- トイレ (*toire*): toilet / bathroom
- バッグ (*baggu*): bag
- シャツ (*shatsu*): shirt
- ズボン (*zubon*): trousers (from French *jupon*)
The traps: words that don't mean what you think
Not all gairaigo maps neatly back to its English origin. Some words have drifted in meaning, shortened to abbreviations, or blended from multiple languages in ways that make them hard to recognize. These are worth knowing specifically so they don't throw you off:
マンション (*manshon*) doesn't mean mansion. In Japan it refers to a mid-to-high-end apartment or condominium. A regular apartment is アパート (*apāto*).
コンセント (*konsento*) doesn't mean consent. It means electrical outlet, from "concentric plug," an old electrical term.
スマート (*sumāto*) doesn't mean smart (as in intelligent). It means slim or slender. Calling someone スマート is a compliment about their figure, not their brains.
ナイーブ (*naību*) doesn't mean naive in the critical English sense. In Japanese it carries the meaning of "sensitive" or "fragile," closer to thin-skinned than gullible.
サービス (*sābisu*) often means something free or complimentary, a little extra the shop gives you. "これはサービスです" means "this one's on the house."
ペット (*petto*) does mean pet, but the colloquial abbreviation ペットボトル (*petto botoru*) means plastic bottle. If someone asks you to throw away the ペット, they mean the bottle.
These mismatches aren't common enough to undermine the system. Most gairaigo means exactly what you'd expect. But when a word you recognize reads strangely in context, meaning drift is the first thing to suspect.
How to decode a word you've never studied
The most useful skill that comes from learning the phonetic rules isn't reading words you've already memorized. It's making an educated guess at words you haven't. The approach I use:
1. Read the katakana out loud, even mentally. The shape on the page is less useful than the sound.
2. Replace R with L wherever it sounds more natural.
3. Drop any trailing vowels added to make the word fit Japanese phonetics: *desuku* → *desk*, *tesuto* → *test*.
4. Collapse long vowels: *kōhī* → *koohii* → coffee.
5. Replace B with V if the B version sounds wrong: *bideo* → video.
It doesn't always work. Some words are too compressed or too far from their origin to decode reliably by ear. But it works more than you'd think, and the habit of running through the rules becomes fast with practice.
One thing that helps: read katakana text out loud whenever you come across it, even when you already know the word. The more you hear Japanese loanwords as sounds rather than as visual symbols, the more naturally the decoding works in reverse.
A note on non-English loanwords
Not all gairaigo comes from English. Japanese has borrowed from Portuguese (パン *pan*, bread; カルタ *karuta*, playing cards), Dutch (ガラス *garasu*, glass; ポンプ *ponpu*, pump), French (アンケート *ankēto*, questionnaire; ブランド *burando*, brand), and German, especially in medical and academic vocabulary (アルバイト *arubaito*, part-time job, from *Arbeit* meaning work).
These follow the same phonetic rules. The sound shift logic is consistent regardless of the source language. What changes is which English substitutions to reverse. If a katakana word doesn't parse as English, trying French or German pronunciation often unlocks it.
Where to go from here
If you haven't finished learning all 46 katakana yet, Understanding Katakana covers the full character set and the confusing pairs that trip people up most. The sound shifts in this article will make more sense once reading the script itself is automatic rather than effortful.
Once you're comfortable with gairaigo, the next real challenge is Japanese words written in native script, first in hiragana, then kanji. The 5 Essential Japanese Phrases article is a good place to start absorbing words that have no English equivalent. And if you want vocabulary that specifically appears in real-world context rather than just on flashcards, reading menus, signs, and product packaging is the fastest accelerant. Gairaigo gives you an entry point into all of it.