To whom it may concern

Writers often miss subject-verb agreement when a singular subject sits next to a base-form verb: The dog chase the cat. The fix is simple once you spot the pattern: use chases for third-person singular subjects.

Below are a compact rule, quick checks, realistic examples (work, school, casual), three-step rewrites, memory tricks, and common confusions to watch for.

Quick answer

Use chases with the singular noun the dog: The dog chases the cat. In the present simple, most third-person singular subjects (he, she, it, or a singular noun) add -s or -es to the base verb.

Wrong: The dog chase the cat.
Right: The dog chases the cat.
Quick check: Is the subject singular? If yes, add -s or -es to the verb in present simple.

Core grammar: why "the dog chases" is correct

Third-person singular subjects require the verb to take -s or -es in the present simple. Identify the subject, decide if it's singular or plural, then match the verb. Phrases between subject and verb don't change agreement.

Compound subjects: The dog and the cat chase (plural) vs. The dog chases (singular).
Intervening phrases: The dog, along with the puppies, chases the squirrel - the verb matches the main subject.
Hyphenated nouns: Treat them grammatically, not visually - my sister-in-law writes (not write).

Common mistakes: six quick wrong/right pairs

Read the right-hand sentences aloud to hear the natural verb form. These patterns repeat in conditionals, questions, and embedded clauses.

Wrong: The dog chase the cat every evening.
Right: The dog chases the cat every evening.
Wrong: Why the dog chase the bicyclist baffles my neighbor.
Right: Why the dog chases the bicyclist baffles my neighbor.
Wrong: If the dog chase squirrels, it will get muddy.
Right: If the dog chases squirrels, it will get muddy.
Wrong: When the dog chase, the whole neighborhood looks up.
Right: When the dog chases, the whole neighborhood looks up.
Wrong: The dog chase the delivery driver every morning.
Right: The dog chases the delivery driver every morning.
Wrong: Does the dog chase birds in this park?
Right: Does the dog chase birds in this park? (question form unchanged)

Real usage

Work

Agreement errors in professional writing can undermine credibility. Apply the quick check before sending emails or reports.

Usage: Please note: The dog chases the new delivery route and may slow down the courier.
Usage: In the incident report, record whether the dog chases company vehicles or just approaches them.
Usage: The safety memo states that the dog chases unfamiliar people and should be fenced off during business hours.

School

Teachers spot subject-verb mismatches quickly. In exams, replace the noun with he/she/it to test the verb form.

Usage: Observation 3: The dog chases the remote-controlled car during the trial.
Usage: In my short story, the dog chases its shadow across the yard.
Usage: Answer: The dog chases the squirrel because it reacts to movement.

Casual

Quick messages and captions often contain this slip. Fixing the verb keeps tone intact while improving clarity.

Usage: My new pup: The dog chases everything on wheels 😂
Usage: Heads up - the dog chases anyone who comes near the porch.
Usage: Watch out! The dog chases bikes along this trail.

Try your own sentence

Test the full sentence, not just the phrase: context usually makes the correct form obvious. Replace the subject with he/she/it to check whether the verb needs -s.

Rewrite help: fix your sentence in three steps

Simple routine: (1) find the subject; (2) decide if it's third-person singular; (3) change the verb and reread. If an auxiliary or modal is present, adjust the main verb accordingly.

Tip: Modal or auxiliary present? The dog can chase (modal + base verb) is correct; with does, use base verb: Does the dog chase?

Rewrite:
Original: The dog chase the cat. → The dog chases the cat.
Rewrite:
Original: When the dog chase, I close the gate. → When the dog chases, I close the gate.
Rewrite:
Original: If the dog chase the postman, call us. → If the dog chases the postman, call us.

Memory trick and quick checks

Mnemonic: "Singular adds S" - link the S in singular to the S at the end of verbs like chases. Use the swap test: replace the noun with he/she/it.

Swap test: The dog → It chases? If yes, use chases.
Nearer-subject rule: With either/or and neither/nor, match the verb to the closer subject.
Intervening phrases like along with or as well as don't change the verb number; scope the main subject instead.

Similar mistakes and common confusions

The same rule applies to other verbs: run/runs, jump/jumps, write/writes. Watch for question inversion and auxiliaries, which change word order but not agreement.

Wrong: The dogs chases the cat.
Right: The dogs chase the cat.
Wrong: Do the dog chase the cat?
Right: Does the dog chase the cat?
Watch: Hyphenated and compound nouns follow grammatical number - my brother-in-law writes, not write.
Spacing note: Extra words between subject and verb can distract you; strip the sentence to subject + verb to test agreement quickly.

FAQ

Is "The dog chase" ever correct?

Not in standard present simple for third-person singular. You may encounter it in dialect, poetic compression, or transcription errors, but the standard form is The dog chases.

Why do I write "he chases" but "they chase"?

He/she/it (third-person singular) takes -s/-es in the present simple. Plural subjects like they use the base verb without -s.

How do I fix the sentence quickly when editing?

Find the subject, swap it with he/she/it, and see whether the verb needs -s. Also check for auxiliaries like does or modals like can.

What about questions: "Does the dog chase" vs "Do the dog chase"?

Use does for third-person singular: Does the dog chase the cat? Do is for plurals: Do the dogs chase the cat?

Can a grammar checker catch this error reliably?

Most modern checkers spot subject-verb agreement, but complex clauses can confuse them. Combine a tool with the simple manual checks above for best results.

Check your sentence in seconds

For a quick second look, paste your sentence into a grammar checker that highlights agreement mistakes and suggests rewrites. Tools can flag "The dog chase" and offer "The dog chases" with brief explanations so you learn while you fix.