Most English speakers learned it second. That is the whole point of it.

Why English ended up as the default

Because enough institutions wrote it into their rules that opting out became expensive. The clearest case is aviation. The International Civil Aviation Organization requires every pilot and air traffic controller on international operations to hold English proficiency at Level 4 on its six-point scale, and from January 2026 that certificate extends to ground operations staff. Two aircraft from two countries meet over a third country and speak English, by regulation.

Science went the same way without a rule. A 2025 bibliometric study found 85 percent of roughly 5 million articles indexed across the natural, medical and social sciences in 2023 were published in English. That share has actually fallen from 94 percent in 1990 as Indonesian, Portuguese and Spanish publishing grew. Citation tells a starker story: 98.89 percent of all cited references are in English. You can publish in your own language; you will mostly be read in English.

English is also official in 58 sovereign states, plus a couple of dozen territories, though published counts run from about 50 to 86 depending on whether de facto status and non-sovereign territories are included. It is a genuinely disputed number rather than one anybody is hiding.

Is English actually an easy language?

The grammar is unusually light and the spelling is unusually bad, and most people meet both facts in that order. English has almost no inflection: nouns take no case endings, adjectives never agree with anything, there is no grammatical gender, and one definite article covers every noun in the language. A German or Russian learner spends the first month noticing how much they do not have to memorise.

Then comes spelling, where the regularity ends. English kept the spellings of words it borrowed across a thousand years and from every direction, so the writing gives you only a rough hint at the sound. This is the reverse of Spanish, where seeing a word tells you how to say it.

And then comes the size of the vocabulary. The Oxford English Dictionary's second edition has full entries for 171,476 words in current use, plus 47,156 that have fallen out of it. The current online dictionary claims over 600,000 forms across the history of the language. Comparisons with other languages are contested, because dictionaries count differently and German builds compounds where English writes two words, so treat any ranking with suspicion. The practical fact stands on its own: English gives you several words where one would do, and choosing between them is a vocabulary problem, not a grammar problem.

Who finds English hardest, and why?

Japanese speakers have the most documented struggle. In the 2025 EF English Proficiency Index, Japan ranked 96th of 123 countries in the Very Low band, an eleventh consecutive year of decline. The reasons are structural. Japanese puts the verb last and English puts it in the middle. Japanese has no articles at all, so a and the have no anchor to attach to. And Japanese has a single liquid consonant covering the ground English splits between r and l, which research shows even highly fluent adult bilinguals struggle to hear reliably as separate speech sounds.

Arabic speakers face a different wall. Several English consonants, including p, v and the ng sound, do not exist in Arabic, and English's vowel inventory maps poorly onto Arabic's smaller one. Written Arabic normally omits short vowels, and peer-reviewed reading research links this to a vowel-blindness effect: Arabic-first readers decoding English lean on the consonants and under-read the vowels. In the 2025 EF index, Saudi Arabia ranked 115th of 123, with most surveyed Middle Eastern countries in the lower half.

Mandarin speakers hit tense. Mandarin has no grammatical tense, so had retired, retired and has retired all correspond to one Chinese form. A 2024 study in the journal Language Learning found Chinese-first learners of English do not process the temporal meaning of English tense while reading in real time, even when their explicit knowledge of the rule is excellent. Stress is the second problem: Mandarin uses tone to distinguish words, so English lexical stress has to be built from scratch.

One honest complication. Korean sits in the same hardest band as Japanese on the Foreign Service Institute's distance scale, yet South Korea ranked 48th of 123 in the 2025 EF index, in the Moderate band. Linguistic distance and measured national proficiency are two different things, and teaching investment moves the second one. Distance from English predicts effort, not outcome.

What advanced English learners are actually missing

Words, almost always. Someone at B2 who has stopped improving usually has the grammar they need and reads well enough to follow an article. What stalls is the gap between recognising a word and being able to produce it in a sentence at conversation speed.

That gap is what spaced review is for. It is also why English is worth treating as a language you collect words in, rather than a language you finish. The words that separate fluent from professional are precise, low-frequency and easy to lose again, which makes them exactly the kind that need to come back on a schedule.

How Koboshi helps with English

• Save an English word from anything you are reading, by typing it or by screenshot, without leaving what you were doing.
• Each card carries the meaning in your own language alongside the English, so a precise word does not get pinned to a rough translation.
• Save a word straight from a chat with ChatGPT, Claude, Claude Code, Codex or Gemini CLI, at the moment the AI uses a word you did not know.
• Review timing follows how well you actually recalled each word, so the ones that keep slipping come back more often.
• English can be one of several languages in the account, each with its own schedule, rather than the only one.

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