You already switch between formal and informal English in your own language without thinking about it. You don’t text a close friend the way you’d write to a bank, and you don’t greet your manager the way you greet your flatmate. The problem is that in a second language those instincts don’t carry over automatically — so learners end up writing emails that read like text messages, or speaking to friends in a way that comes across as stiff and cold. Getting this level of formality right, what teachers call ‘register’, matters more than most people realise. Your English can be completely correct and still land badly.
What ‘register’ actually means
Register is simply how formal or casual you choose to be for a given situation. English doesn’t have the built-in formal and informal ‘you’ that French or German rely on, so we signal formality in quieter ways — through word choice, contractions, and how directly we ask for things. ‘Could you possibly send me the report?’ and ‘Send me the report’ ask for exactly the same thing, but they belong in completely different situations. Fluency isn’t only about being correct; it’s about sounding right for where you are and who you’re talking to.
The words that give it away
The fastest way to shift register is vocabulary. English is full of pairs where one word is everyday and the other is formal — usually because one comes from old Anglo-Saxon roots and the other from Latin or French. ‘Ask for’ and ‘request’. ‘Get’ and ‘receive’. ‘Buy’ and ‘purchase’. ‘Help’ and ‘assist’. ‘Need’ and ‘require’. ‘Sorry’ and ‘I apologise’. The everyday word isn’t wrong in a formal message, but a few of the formal ones signal respect and professionalism. Phrasal verbs tend to lean casual (‘find out’, ‘put off’, ‘sort out’), while their one-word cousins (‘discover’, ‘postpone’, ‘resolve’) lean formal. You don’t need to memorise long lists — just start noticing the pairs when you read.
Contractions, greetings and the small signals
Beyond vocabulary, a handful of small habits do most of the work. Contractions (‘I’m’, ‘don’t’, ‘we’ll’) are natural in speech and friendly emails, but usually written out in full in formal documents (‘I am’, ‘do not’). Greetings matter too: ‘Hi Sam’ for a colleague, ‘Dear Ms Patel’ for someone you don’t know, and never ‘Hey’ on a job application. Formal English also drops slang, abbreviations and emoji — no ‘gonna’, no ‘ASAP’ in a cover letter. And formal requests get softer and longer rather than blunter: ‘I was wondering if you might be able to…’ sounds more polite than ‘Can you…’, even though it means the same thing. If formal writing is where you feel least sure, our guide to writing professional emails in English takes this further.
So when do you use which?
Go formal when the distance or the stakes are high: job applications, emails to people you don’t know, academic work, official complaints, anything with your professional name attached. Go informal with friends, close colleagues, social media and everyday chat. Most of real life actually sits in the middle, in a neutral register that’s polite but relaxed — which is where the majority of workplace English lives. When you’re unsure, aim slightly more formal than you think you need; it’s far easier to warm a message up than to walk back something too casual. And read the room: match the formality of whoever wrote to you first.
How to build the instinct
You develop a feel for register the same way native speakers did — by noticing it. When you read an email, a news article or a message from a friend, ask yourself why it sounds formal or casual, and which exact words are doing the work. Keep two versions of the phrases you use most, one buttoned-up and one relaxed, and practise rewriting a casual note as a formal one and back again. Do that a few times and the switch stops feeling like a decision — it starts happening on its own, which is exactly what you want.
Register is one of those quiet skills that separates learners who are merely correct from those who sound genuinely fluent, and it’s hard to master alone, because you often can’t hear when you’ve got it slightly wrong. If you’d like a teacher to show you where your English is too stiff or too casual and help you find the right tone for work, exams and everyday life, take a look at the courses at Kensington English — our small online classes work on exactly this kind of real-world English.
