What makes a complete sentence?
Every complete English sentence needs three ingredients:
- A subject — the noun (person, place, thing, or pronoun) that the sentence is about.
- A predicate — the verb (and everything attached to it) that says what the subject does or is.
- A complete thought — the sentence must stand on its own. It shouldn't leave the reader dangling.
The classic three-word example: David slept. Subject = David. Predicate = slept. Complete thought = yes. But David went. is technically subject + verb yet leaves you asking went where? — so it's arguably incomplete depending on context. Real writing lives in that grey zone; this checker calls out the clearer cases and lets you judge the rest.
The four fragment types this checker detects
| Type | What's missing | Fragment example | Suggested fix |
|---|---|---|---|
| Missing subject | No noun performing the action | Ran through the entire dataset overnight. | The script ran through the entire dataset overnight. |
| Missing verb | Only a noun phrase; no action | The new marketing strategy for Q3. | The new marketing strategy for Q3 launches next Monday. |
| Dependent clause alone | Starts with a subordinating word (Because, Although, When, If…) | Because the client changed the requirements at the last minute. | The timeline shifted because the client changed the requirements at the last minute. |
| Verbal phrase | Starts with an -ing or infinitive form used as a phrase, not a main verb | Running the numbers on last quarter's revenue. | The analyst was running the numbers on last quarter's revenue. |
Run-on sentences (bonus)
A run-on isn't just a long sentence — it's two or more independent clauses joined without correct punctuation or a coordinating conjunction. I finished the report I sent it to my manager. is a run-on because I finished the report and I sent it to my manager are two complete sentences smashed together. Fixes: add a period, add a semicolon, or add a comma + conjunction (I finished the report, and I sent it to my manager.). The checker flags likely run-ons in amber.
When fragments are actually okay
Not every fragment is a mistake. Skilled writers use fragments deliberately for rhythm, punch, and dialogue:
- Advertising: "Just do it." "The best decision we ever made."
- Dialogue: Realistic speech rarely uses full sentences.
- Creative writing: A one-word fragment after long sentences creates emphasis.
- Journalistic hooks: "Rain. Again. For the fifth day straight."
Fragments are inappropriate in academic essays, legal writing, business reports, and formal documents where structure signals rigor. Use the checker to find your fragments, then decide which to keep.
How the checker works
The tool applies a rules-based analysis (no AI, no server calls). For each detected sentence it looks for:
- A capitalized first word.
- Ending punctuation (. ! ?).
- At least one noun/pronoun candidate (the subject).
- At least one verb candidate (the predicate).
- A leading subordinator (Because, Although, When, If, Since…) that would make the whole clause dependent.
- An -ing or to + verb opening that would make it a verbal phrase.
- Two consecutive independent clauses without a conjunction (run-on signal).
This is heuristic, not perfect. Where the checker is unsure it errs toward marking a sentence complete — the goal is to catch the obvious problems, not to argue every edge case.
When you need this
- Essays and papers. Catch fragments before your instructor does.
- Business writing. Formal reports lose credibility when they contain fragments.
- Legal documents. Ambiguity from a fragment can matter enormously.
- Web copy audits. Decide which fragments serve rhythm and which are typos.
- ESL and grammar practice. The verdict-plus-fix pattern makes the rule tangible.
Frequently asked questions
What is a sentence fragment?
A group of words punctuated as a sentence but missing a subject, verb, or complete thought. Fragments look like sentences (capital letter, ending punctuation) but don't stand on their own.
What are the common types of sentence fragments?
Four: missing subject, missing verb, dependent clause standing alone, and verbal phrase. See the table above for examples of each with suggested fixes.
Are fragments always wrong?
No. Advertisers and creative writers use them deliberately for emphasis. In academic and business writing they usually signal an editing error.
What is a run-on sentence?
Two or more independent clauses joined without correct punctuation. Fix with a period, semicolon, or comma-plus-conjunction.
Does it check spelling or agreement?
No — this tool checks sentence structure only (fragment vs complete vs run-on). Use a dedicated grammar checker for spelling, tense, and agreement.
Can it be wrong?
Yes. English syntax has plenty of edge cases. When the rule-based logic is unsure, the checker marks a sentence complete rather than throw a false-positive fragment.
Does it save my text?
No. Everything runs in your browser. Nothing is uploaded or stored.
Related tools
References
- Purdue OWL — "Sentence Fragments" and complete-sentence requirements (subject, predicate, complete thought).
- UNC Writing Center — "Fragments and Run-ons" (the classic three-part rule).
- Chicago Manual of Style — Guidance on when fragments are stylistically acceptable.