Run-ons and Fragments

Simple explanation

Two sentence mistakes are more common than any other in written English:

1. Run-on sentence — two complete thoughts joined without the right punctuation or connecting word.
2. Fragment — an incomplete thought that stops before it is a full sentence.

Both make writing confusing. Both are easy to fix once you can see them.

Why it matters

Run-ons make readers rush and feel confused. Fragments make readers feel like they are missing something. Both break the rhythm of professional writing. Learning to catch them — quickly, on your own — is one of the biggest jumps in writing quality.

Part 1 — Run-on sentences

A run-on happens when two complete sentences are joined without the right glue.

Three common types:

Type 1 — No punctuation at all (fused sentence):

✗ "The meeting was long I was exhausted by the end."

Two separate thoughts: (1) The meeting was long. (2) I was exhausted by the end. They need something between them.

Type 2 — Only a comma (comma splice):

✗ "The meeting was long, I was exhausted by the end."

A comma alone is too weak to join two full sentences.

Type 3 — Too many thoughts in one sentence:

✗ "I finished the report and I sent it to the team and they replied and we had a call."

This is technically correct but reads like one breathless sentence with no structure.

How to fix a run-on

You have four options. Use the one that fits the idea best.

Fix	Example
Add a full stop — make two sentences	The meeting was long. I was exhausted by the end.
Add a comma + joining word (and, but, so, yet)	The meeting was long, so I was exhausted by the end.
Add a semicolon (for closely related ideas)	The meeting was long; I was exhausted by the end.
Rewrite with a connecting word (because, although, when)	Because the meeting was so long, I was exhausted by the end.

Part 2 — Sentence fragments

A fragment is a group of words that starts like a sentence but does not finish the thought. It is missing something — usually a subject, a verb, or a complete idea.

Three common types:

Type 1 — Missing a subject:

✗ "Finished the report early."

Who finished it? Add a subject: "She finished the report early."

Type 2 — Missing a verb:

✗ "The report on the new product launch."

What happened to it? Add a verb: "The report on the new product launch is ready."

Type 3 — Dependent clause alone (the most common type):

✗ "Because I was running late."

This starts with because, which means it needs another clause to complete it:

✓ "Because I was running late, I joined the call from my phone."

Words like because, although, when, since, if, unless, before, after make a clause dependent. A dependent clause cannot stand alone as a sentence — it always needs a main clause.

When a fragment is acceptable

In creative writing, fiction, or informal writing, short fragments are sometimes used for effect or rhythm:

"He opened the email. Three words. All in capitals."

In formal writing — reports, emails, academic work — avoid them. In conversation and informal writing, they are common and fine.

Daily life usage — spot and fix

1. Run-on: "Please review the attached file it contains the final numbers." → Fixed: "Please review the attached file. It contains the final numbers."
2. Fragment: "Although she had more experience." → Fixed: "Although she had more experience, the role went to someone else."
3. Run-on: "I wasn't sure about the deadline I asked my manager." → Fixed: "I wasn't sure about the deadline, so I asked my manager."
4. Fragment: "The new policy on remote work." → Fixed: "The new policy on remote work takes effect next month."

Practice quiz

Quick summary

• Run-on = two complete sentences joined without the right punctuation. Fix with a full stop, a comma + joining word, a semicolon, or a rewrite.
• Fragment = an incomplete sentence. Fix by adding the missing subject, verb, or completing the dependent clause.
• Words like because, although, when, since, if start dependent clauses — they cannot stand alone.
• In formal writing: no fragments, no run-ons. In casual writing, short fragments are sometimes acceptable for effect.