undos (undoes)

Short answer: For third-person singular subjects (he/she/it) use "undoes," not "undos."

Quick answer

"Undos" is incorrect for the third-person singular present. Use "undoes."

Third-person singular (he/she/it) + verb ending in -o → add -es: undo → undoes.
I/you/we/they use the base form: I undo, you undo, they undo.
If the subject is he/she/it, write "undoes."

Core rule

In the simple present, most verbs add -s for third-person singular. If a verb ends in -o (or -ch, -sh, -x, -s, -z), add -es. So: undo → undoes (like do → does, go → goes).

Check the subject: is it he/she/it? If yes, add -s or -es as the rule requires.
Shortcut: swap in "do"-if you would use "does," use "undoes."

Common wrong/right pairs (fast reference)

Quick correction pairs you can copy when proofreading.

Wrong: He undos the configuration after testing.
Right: He undoes the configuration after testing.
Wrong: It undos the change at midnight.
Right: It undoes the change at midnight.
Wrong: She undos the merge when conflicts appear.
Right: She undoes the merge when conflicts appear.
Wrong: The script undos files older than seven days.
Right: The script undoes files older than seven days.
Wrong: Manager undos the approval without notice.
Right: The manager undoes the approval without notice.
Wrong: The policy undos previously allowed exceptions.
Right: The policy undoes previously allowed exceptions.

Typical contexts: work, school, casual

Real sentences where the error commonly appears, with fixes.

Work - Wrong: The deployment undos the hotfix automatically.
Right: The deployment undoes the hotfix automatically.
Work - Wrong: He undos the permissions after the audit.
Right: He undoes the permissions after the audit.
Work - Wrong: She undos the draft without saving comments.
Right: She undoes the draft without saving comments.
School - Wrong: Professor undos the experiment when results are invalid.
Right: The professor undoes the experiment when results are invalid.
School - Wrong: He undos his corrections in the lab notes.
Right: He undoes his corrections in the lab notes.
School - Wrong: The script undos previous runs between trials.
Right: The script undoes previous runs between trials.
Casual - Wrong: Mom undos my passwords again.
Right: Mom undoes my passwords again.
Casual - Wrong: She undos the message before I read it.
Right: She undoes the message before I read it.
Casual - Wrong: It undos the filter when the app updates.
Right: It undoes the filter when the app updates.

Rewrite help: 3 copyable repairs

Original → grammatical fix → polished rewrite you can paste.

Original: She undos her mistakes before submitting her work.Fix: She undoes her mistakes before submitting her work.Polished: She reviews and undoes mistakes before submitting her work.
Original: He undos the shortcut and starts again.Fix: He undoes the shortcut and starts again.Polished: He removes the shortcut and restarts the process.
Original: The system undos the last commit without logging the reason.Fix: The system undoes the last commit without logging the reason.Polished: The system automatically reverts the last commit and logs the reason.

Try your own sentence

Test the whole sentence rather than the word alone. Context makes the correct form clear: if the subject is he/she/it, change "undo" to "undoes."

Memory trick and 2-minute practice

Mnemonic: pair undo with do. If you would say "does" for do, say "undoes" for undo.

Drill: swap "undo" with "do" in three sentences-if "does" fits, use "undoes."
Quick edit: search your document for "undos" and replace with "undoes" where the subject is he/she/it.
Practice: write three sentences with he/she/it + verbs ending in -o and add -es.

Similar mistakes to watch for

Other -o verbs need -es in third-person singular. Also note irregular past tense.

Common confusions: dos (wrong) vs does (right); gos (wrong) vs goes (right).
Past tense: undo → undid (not "undoed").
Watch made-up forms: "undos" and "undoed" are wrong in standard English.

Wrong: He gos to the office every day.
Right: He goes to the office every day.
Wrong: She dos the experiment each week.
Right: She does the experiment each week.
Wrong: They undoed the change yesterday.
Right: They undid the change yesterday.

Hyphenation, spacing and grammar checks

This is a conjugation issue, not hyphenation or spacing. Do not write "un-dos" or "un dos." Keep the verb as one word: undoes.

Fast checklist: (1) find "undos" in your document, (2) confirm the subject is he/she/it, (3) replace with "undoes" or reword.

Fix spacing and layout after correcting the verb if needed.
Basic spellcheckers can miss plausible typos; use a grammar-aware tool for conjugation errors.
Wrong: She un dos the command.
Right: She undoes the command.

Grammar troubleshooting and tools

Manual: scan for verbs ending in -o, highlight third-person singular subjects, and add -es. Automated: use a grammar-aware checker or browser extension to flag conjugation mistakes as you type.

Manual shortcut: replace the verb with "do"-if "does" is needed, change "undo" to "undoes."
Use a grammar extension to highlight "undos" and suggest "undoes" where appropriate.
Paste suspect sentences into a grammar checker to confirm the correction.

FAQ

Is "undos" ever correct?

Not as the third-person singular present of "undo." It may appear in names, code variables, or typos, but not in standard English grammar.

Why do writers use "undos"?

They overapply the simple -s rule or type phonetically. Fast typing and unfamiliarity with the -es rule for verbs ending in -o cause the error.

What's the past tense of "undo"?

The past tense is "undid." Do not write "undoed." Example: She undid the change yesterday.

Will a spell checker catch "undos"?

Basic spell checkers might not flag it because "undos" looks plausible. A grammar-aware tool catches conjugation errors more reliably.

Quick proofreading trick?

Swap in "do": if the sentence calls for "does," change "undo" to "undoes." Also search your document for "undos" and review each occurrence.

Need a quick check?

When in doubt, paste the sentence into a grammar checker or search your document for "undos" and correct instances where the subject is he/she/it.

Using a grammar extension saves time and prevents the error from recurring.