Starting a sentence with "And" or "But" is something many writers avoid, not because it's wrong, but because a teacher once told them it was. That instruction had good intentions. It doesn't have good grammar behind it. Both words belong at the start of a sentence whenever the sentence calls for them, and the evidence for that stretches back to the King James Bible, Shakespeare, and every major style guide published in the past 30 years.
Where the rule came from
The prohibition dates to the 19th century, when elementary school teachers used it as a blunt tool to stop children writing run-on sentences like: "We went to the park. And we played. And we ran. And we got chips." That's a valid classroom concern. It has nothing to do with grammar. It's a lesson about variety and structure, dressed up as a rule.
No major style authority supports the ban. The Chicago Manual of Style states plainly that there's no reason not to begin a sentence with "And" or "But." The AP Stylebook takes the same position. Merriam-Webster's usage notes go further, pointing out that the construction appears in formal writing throughout the history of English. The rule was invented by educators, not grammarians.
What "And" and "But" actually do at the start of a sentence
Both words are coordinating conjunctions. Their job is to link ideas. When a conjunction starts a sentence, it links the new sentence to the one before it, creating a tight logical connection. That's not an error. It's a rhetorical choice.
"And" at the start of a sentence adds emphasis or continuation:
- "The client approved the proposal. And the board signed off the same afternoon." The second sentence lands harder as a standalone.
- "We cut costs by 12 percent. And we did it without a single redundancy." The "And" gives the second fact its own weight.
"But" at the start of a sentence signals a direct contrast:
- "The report is detailed. But it doesn't answer the one question the CFO asked."
- "She agreed in principle. But the timeline still needed to be resolved."
In both cases, the conjunction-led sentence is cleaner and more direct than the alternative. You could write "however" or "nevertheless" instead, but those words slow the sentence down and add a formal weight that isn't always warranted. Short and punchy often beats long and hedged.
When starting with "And" or "But" actually improves the writing
Three situations push strongly in favour of the conjunction opener.
When you want contrast to hit hard. "But" at the start of a sentence gives the opposition its own line. Burying it inside a compound sentence softens the contrast. If the contrast is the point, give it space.
When you're writing at speed and your reader is too. Business writing is read under time pressure. Short sentences with clear logical connectors move faster than long compound constructions. A "But" opener tells the reader instantly: this sentence contradicts what came before. No parsing required.
When the previous sentence ends on a strong claim. A claim followed by "And" or "But" creates momentum. The reader knows the next idea connects directly. It keeps them reading. This matters in emails, proposals, and executive summaries, where losing the reader after the second sentence is a real risk. If you want to sharpen those opening paragraphs, the same logic applies to how to write a business email opening line: every sentence after the first either builds momentum or kills it.
The cases where you should reconsider
Correct doesn't mean always appropriate. A few situations warrant caution.
Formal legal or regulatory documents. Some legal drafting conventions are conservative by design. If a document will be reviewed by a compliance team or filed with a regulator, check the house style before defaulting to your own preference. The rule isn't wrong; the audience is what matters.
Overuse. Starting three consecutive sentences with "And" or "But" is rhythmically clunky. The trick is that the conjunction opener works because it creates emphasis through variation. If every sentence starts that way, there's nothing to vary from.
When the connection isn't real. "But" implies genuine opposition. Don't use it for mild caveats that don't actually contradict what came before. "The report is thorough. But it's formatted well." That's not a contrast. That's just two positive statements. Use "And."
How this fits broader punctuation habits
The anxiety around "And" and "But" openers is part of a wider tendency to treat style preferences as grammar rules. The same happens with the Oxford comma, with split infinitives, and with ending sentences on prepositions. None of those are errors. They're choices, and good writers make choices deliberately rather than by reflex.
One related habit worth checking: the comma that connects two independent clauses with "but" inside a single sentence. That one does follow a specific rule. If you're working through your comma placement, the guide on using a comma before and after "but" covers the mechanics in full.
The underlying principle is the same in both cases: understand what a word or punctuation mark actually does, then decide whether the sentence needs it. That's more useful than following a prohibition that was never a rule to begin with.
A quick reference
Use "And" to start a sentence when you want to add emphasis to a second related point, or when you want the second idea to feel like a distinct beat rather than a continuation of the same thought. Use "But" to start a sentence when the contrast is the main message and you want it to land with full force. Avoid either opener when formality is explicitly required by the format or the client, and don't cluster them in consecutive sentences. That's the whole rule.