Translating Japanese slang and wasei-eigo: When English takes on new meaning

English has influenced the Japanese language for decades, particularly across business, technology and popular culture. This influence is especially visible in modern Japanese slang and the English-inspired expressions used in everyday conversation. 

However, English-sounding words used in Japanese don’t always carry the meanings that most English speakers would expect. This is especially true of wasei-eigo — expressions that use English words and sounds, but were created in Japan and shaped by the Japanese language and culture.

Japanese slang takes many forms, but wasei-eigo is one of the most common and most challenging for translators, largely because its initial familiarity can be misleading. Words that appear recognisable may be used in different ways, or carry meanings that don’t exist in English. As a result, wasei-eigo (and English-derived slang as a whole) presents a real challenge for translation and localisation.

What is wasei-eigo?

Wasei-eigo (和製英語) literally means “English made in Japan”. It refers to words and expressions that are based on English, but were created by Japanese speakers and do not exist in the same form (or with the same meaning) in standard English. In everyday use, wasei-eigo often overlaps with Japanese slang, particularly in informal speech, workplace language and digital communication.

These terms are often formed using familiar English words or sounds, which is why they can appear immediately understandable to English speakers. In practice, however, their meaning is shaped by Japanese cultural context and linguistic structure. As a result, wasei-eigo may express ideas that English can’t, or use English-derived words in unexpected ways.

What is gairaigo?

While discussing wasei-eigo, it’s important to distinguish it from gairaigo (外来語), another common category of foreign-derived words in Japanese. While these terms are often grouped together, they function very differently.

Similar to wasei-eigo, gairaigo refers to words adopted from other languages (including English). However, unlike wasei-eigo, the meanings of gairaigo words are broadly similar to their original form. 

Cultural & historical roots of wasei-eigo

Wasei-eigo didn’t develop in isolation. Its growth is closely linked to Japan’s increased exposure to Western culture from the late 19th century onwards, and more noticeably following the Second World War. In Japan, English became strongly associated with progress, innovation and global relevance, especially in sectors such as technology, business and entertainment.

Rather than adopting English in its original form, Japanese speakers adapted it to fit their own linguistic structure. New expressions emerged to describe concepts that felt modern and international, but that also aligned with Japanese patterns of communication. Over time, these English-inspired terms became embedded in everyday language, from workplace settings to casual conversation.

Wasei-eigo in context: Where literal translations fall short 

One of the reasons wasei-eigo causes confusion is that it often looks easier to understand than it really is. Because these expressions are built from English words and sounds, it can be tempting to translate them directly, but this doesn’t work.

Take the following examples:

• コスパ  (pronounced: “kosupa”)
  Short for ‘コストパフォーマンス’ (pronounced: “kosutopafōmansu”), a literal translation might focus on the idea of ‘cost performance’, which in English can refer to the financial efficiency of a project. In Japanese, however, “kosupa” means something that offers good value for money.
• ンジニア (pronounced: “njinia”)
  While the word ‘engineer’ exists in English, this term usually refers specifically to a software or IT engineer in Japanese. Without context, a direct translation could misrepresent the role being described.
• ノートパソコン (pronounced: “nōto pasokon”)
  This term is formed from ‘notebook’ and ‘personal computer’, but simply means ‘laptop’ in Japanese. While the English components are recognisable, translating the phrase literally could cause confusion.

Wasei-eigo doesn’t just alter the meaning of English words; it reflects how Japanese speakers interpret and adapt English to suit local usage. For translators and localisation specialists, recognising this gap between appearance and intent is crucial. Accurate translation depends not on recognising familiar words, but on understanding how they function within the Japanese language and culture.

Where assumptions cause problems

The effects of English-derived language in Japanese are often felt most clearly in professional settings. A minor misunderstanding can have a disproportionate impact, particularly when language is used to define people’s roles, describe products or set expectations.

While not all Japanese slang derives from English, the expressions that do are among the most likely to cause misunderstandings for non-Japanese speakers.

In marketing and customer-facing content, subtle shifts in meaning can affect tone and clarity. In internal communication, familiar-looking terms may obscure what is actually being discussed, leading to confusion rather than efficiency. These issues rarely stem from poor translation alone, but from assumptions about shared meaning. Effective localisation accounts for how language is used in practice, ensuring that intent is conveyed clearly rather than relying on surface-level similarity.

A moving target in modern Japanese

As work culture, technology and digital communication continue to evolve, new English-derived expressions are finding their way into Japanese every day. Terms that feel current or efficient can quickly become embedded in professional language, particularly online and in professional settings.

For translators and localisation specialists, this makes ongoing cultural awareness essential. Accurate translation depends not only on understanding established usage, but on recognising how meaning shifts over time as new terms emerge and spread.

What wasei-eigo reveals about effective localisation

Wasei-eigo highlights a broader truth about translation and localisation: shared vocabulary does not guarantee shared meaning. English-derived words in Japanese often feel familiar, but their usage and intent are shaped by local culture.

For businesses communicating across languages, this makes cultural understanding just as important as linguistic accuracy. Effective localisation requires more than translating words, it involves recognising how language is used in context, how meanings evolve, and how easily assumptions can lead to misunderstanding.

By approaching Japanese slang and wasei-eigo with this awareness, translators can move beyond surface-level translations and deliver communication that is clear, natural and appropriate for its audience. In doing so, localisation becomes not just a technical process but a way of bridging cultural gaps with confidence and precision.