Common Grammar Mistakes Made by AI

Everyone · Mistakes to avoid · Updated October 1, 2026 · LearnLife Editorial

Why Does AI Make Grammar Mistakes?

AI models generate text by analyzing vast amounts of data and predicting which words or phrases fit best in a given context. However, they do not truly understand language or its rules—they operate on probabilities, not comprehension. This means AI can misinterpret nuances, idioms, or ambiguous phrases, leading to grammar mistakes. For example, if an AI sees “The team are winning” frequently in its data, it might incorrectly use plural verbs for collective nouns, even when singular verbs are correct in American English.

Additionally, AI training data may contain errors, leading the system to replicate mistakes. Since AI cannot reason about meaning or context like humans, it sometimes chooses grammatically incorrect but statistically common patterns. Understanding these limitations helps users approach AI-generated text critically rather than assuming flawless grammar.

To minimize errors, users should:

• Treat AI output as a draft needing review.
• Compare AI-generated sentences with common grammar rules.
• Use AI as a tool for ideas, not a final authority on correctness.

What Are Common Subject-Verb Agreement Mistakes Made by AI?

Subject-verb agreement errors occur when the verb’s form doesn’t match the subject’s number. AI often struggles with collective nouns, indefinite pronouns, or complex sentence structures. Examples include:

• Incorrect: “The list of items are long.”
• Correct: “The list of items is long.”

• Incorrect: “Everyone have finished their homework.”
• Correct: “Everyone has finished their homework.”

These mistakes can confuse readers and undermine credibility. To avoid them:

1. Identify the true subject of the sentence, not a nearby noun.
2. Remember singular indefinite pronouns like “everyone,” “someone,” “each” take singular verbs.
3. For collective nouns (team, committee), decide if the group acts as one (singular verb) or individuals (plural verb), and adjust accordingly.

When reviewing AI text, ask: “Who or what is performing the action? Is it singular or plural?” This focus helps catch agreement errors AI often misses.

How Does AI Misuse Verb Tenses and What Does It Cost?

Verb tense errors happen when AI shifts tenses inconsistently or chooses the wrong tense for the intended timeframe. For example:

• Incorrect: “She walks to the store and bought milk.”
• Correct: “She walked to the store and bought milk.”

• Incorrect: “I was hungry, so I eat a sandwich.”
• Correct: “I was hungry, so I ate a sandwich.”

Such mistakes confuse readers about when actions occur and interrupt narrative flow. This reduces clarity and professionalism, especially in formal writing.

To fix verb tense mistakes:

• Determine the timeframe of your narrative or description.
• Ensure all verbs align with that timeframe unless signaling a deliberate time shift.
• When editing AI-generated text, highlight all verbs and check tense consistency.
• Revise sentences that mix tenses without clear purpose.

For example, if the sentence describes a past event, convert all verbs to past tense unless referring to a general truth.

What Are Homophone Confusions and How to Prevent Them in AI Writing?

Homophones—words that sound alike but differ in spelling and meaning—trip up AI because it predicts based on common patterns, not meaning. Examples include:

• “Their” (possessive) vs. “There” (place) vs. “They’re” (they are)
• “Your” (possessive) vs. “You’re” (you are)
• “Its” (possessive) vs. “It’s” (it is)

Incorrect use changes the sentence meaning or makes it nonsensical:

• Incorrect: “Your going to love this.”
• Correct: “You’re going to love this.”

• Incorrect: “The dog lost it’s collar.”
• Correct: “The dog lost its collar.”

To catch homophone errors:

• Read the text aloud to see if it sounds right.
• Identify every homophone and verify it fits the sentence meaning.
• Use grammar and spell-check tools that highlight commonly confused words.
• Develop a habit of double-checking homophones, especially in AI-generated text.

Even if AI chooses a common homophone, confirm its meaning matches your intent.

How Does AI Handle Punctuation, and What Mistakes Occur?

Punctuation errors by AI can drastically change sentence meaning or create confusion. Common mistakes include:

• Missing commas that separate clauses: “Lets eat Grandma” vs. “Let’s eat, Grandma.”
• Incorrect apostrophes: “Its a nice day” vs. “It’s a nice day.”
• Misuse of colons and semicolons, leading to run-on sentences or fragments.

Poor punctuation impacts readability, meaning, and professionalism. To avoid this:

1. Learn basic punctuation rules, such as when to use commas, apostrophes, colons, and semicolons.
2. Always review AI-generated punctuation carefully.
3. Use grammar checkers that flag punctuation errors.
4. Read sentences aloud with pauses where punctuation should be to catch missing marks.

For example, inserting a comma after introductory phrases (“After the meeting, we went out”) improves clarity and flow.

Why Does AI Struggle with Pronoun Reference Errors?

Pronouns replace nouns but must clearly refer to one specific noun (antecedent). AI often generates sentences where pronouns are ambiguous, leaving readers unsure who or what is referenced. For example:

• Ambiguous: “John told Mark that he was late.”
• Clear: “John told Mark, ‘You are late.’” or “John told Mark that Mark was late.”

Such ambiguity leads to confusion and misinterpretation. To fix pronoun errors:

• Identify the noun each pronoun should replace.
• If unclear, replace pronouns with the noun for clarity.
• Break complex sentences into simpler ones to clarify references.
• When editing AI output, ask: “Who does this pronoun refer to?”

Clear pronoun references improve the reader’s understanding and text coherence.

What Are Common Sentence Fragment and Run-On Mistakes AI Makes?

AI sometimes generates incomplete sentences (fragments) lacking a subject or verb, or run-on sentences that improperly join independent clauses without correct punctuation or conjunctions.

Examples:

• Fragment: “Because she was late.”
• Run-on: “She was late she missed the bus.”

Fragments confuse readers by leaving thoughts unfinished, while run-ons overload sentences and reduce clarity. To fix:

• Ensure every sentence has a subject and verb.
• Use appropriate conjunctions (and, but, so) or punctuation (periods, semicolons) to separate independent clauses.
• Break long, complicated AI-generated sentences into shorter, clearer ones.

During editing, highlight each sentence and check completeness and punctuation to improve flow and readability.

How Can You Recover If You Have Already Made a Grammar Mistake With AI?

If you realize AI-generated grammar mistakes have been published or submitted, act quickly to correct them:

• Edit digital content or documents to fix errors.
• If corrections aren’t possible (e.g., printed materials), issue clarifications or apologies if necessary.
• Learn from mistakes by reviewing what went wrong and how to spot similar errors next time.
• Keep a checklist of common AI grammar pitfalls for future reference.
• Use multiple editing tools to catch errors before finalizing work.

Developing a habit of thorough proofreading and understanding AI’s limitations will reduce repeated mistakes and improve overall writing quality.

What Habits Prevent Grammar Mistakes When Using AI?

To minimize grammar mistakes from AI, develop these practical habits:

• Proofread AI-generated text carefully before use.
• Read text aloud to detect awkward grammar or unclear meaning.
• Use grammar and spell-check tools alongside AI.
• Learn common AI grammar errors so you can spot them quickly.
• Don’t accept AI suggestions blindly; revise sentences that seem incorrect or awkward.
• Practice writing and grammar skills independently to better judge AI output.
• When in doubt, consult grammar guides or trusted editors.

By combining AI’s strengths with human judgment, users can create clear, accurate writing that avoids common AI grammar pitfalls.

Frequently asked questions

Can AI understand complex grammar rules perfectly?

AI operates by pattern recognition without true comprehension, so it often misses nuanced grammar rules and makes errors, especially with complex sentence structures or exceptions.

Should I trust AI to correct my grammar automatically?

AI can assist with grammar but is not foolproof. Always review AI corrections yourself and use other grammar-check tools for better accuracy.

What is a good tool to spot AI grammar mistakes?

Popular grammar checkers in word processors or apps highlight many AI errors, including punctuation, homophones, sentence fragments, and verb tense inconsistencies.

Why do AI-generated texts sometimes feel awkward or unnatural?

AI predicts words based on likelihood, not meaning, which can produce grammatically correct but contextually odd or unclear sentences that feel unnatural.

How can educators help students avoid grammar mistakes when using AI?

Educators should teach students to critically evaluate AI outputs, recognize common AI errors, and always proofread their work before submission.

Is it okay to depend entirely on AI for writing assignments?

Relying solely on AI risks grammar mistakes and lack of original thought. Use AI as a helpful tool, not a substitute for personal effort and editing skills.