Formal vs Informal Sentences: the rule, with examples
A sentence is more formal when it avoids contractions, slang, and casual phrasal verbs, and uses precise vocabulary instead. “Kids can’t figure it out” is informal; “Students are unable to understand it” is formal. Paste your own sentence into the free checker below to fix it in one click.
A sentence is more formal when it avoids contractions, slang, and casual phrasal verbs, and uses precise vocabulary instead. “Kids can’t figure it out” is informal; “Students are unable to understand it” is formal.
How it works
- 1Spot the pattern. Scan for contractions, first-person asides, vague intensifiers (“really”, “a lot”), and conversational phrasal verbs. The more of these, the more informal the sentence reads.
- 2Apply the rule. Expand contractions, replace phrasal verbs with single formal verbs, and swap casual words for precise ones — without making the sentence stiff or padded.
- 3Check your sentence. Paste your text into the grammar checker below — it flags the issue and shows the correction.
- 4Re-read it. Read the corrected version aloud to confirm it says exactly what you meant.
The rule
Formal writing avoids contractions (“don’t” → “do not”), slang and idioms, and casual phrasal verbs (“find out” → “determine”), while keeping sentences complete and precise.
How to spot it
Scan for contractions, first-person asides, vague intensifiers (“really”, “a lot”), and conversational phrasal verbs. The more of these, the more informal the sentence reads.
How to fix it
Expand contractions, replace phrasal verbs with single formal verbs, and swap casual words for precise ones — without making the sentence stiff or padded.
The most common mistake
Assuming “formal” means “longer”. Formality is about word choice and tone, not length — a formal sentence can still be concise. If you’re not sure whether your sentence has the problem, paste it into the checker above — it catches this and explains the fix in plain language.
| ❌ Incorrect | ✓ Corrected | Why |
|---|---|---|
| Kids these days don’t get it. | Today’s students often struggle to understand it. | No contraction or slang |
| We need to find out what went wrong. | We must determine what went wrong. | Phrasal verb → formal verb |
| The results were pretty good. | The results were satisfactory. | Vague intensifier → precise word |
Frequently asked questions
Which sentence is more formal?
The one without contractions, slang, or casual phrasal verbs. “The committee will not approve the request” is more formal than “They won’t okay it.”
When should I write formally?
Academic essays, cover letters, reports, and professional emails generally call for a formal tone. Personal blogs, social posts, and casual messages do not.
How do I check my own writing for this?
Paste your text into the free grammar checker on this page. It flags the issue, suggests a correction, and explains why — so you learn the rule, not just the fix.
Is it free?
Yes — 3 free runs every day with up to 500 words per run, no credit card to start. Upgrade for a larger word pool, or use the free iOS app.