Swear Doing vs. Swear To Do
Oxford separates the intransitive offensive-language sense from the promise pattern “swear to do.” The page keeps those senses distinct instead of treating “swear doing” as an alternate complement.
Use “swear to do” for a serious promise to perform an action. “Swearing” can also mean using offensive language, but that is a different sense and not a gerund complement after “swear.”
Key details
Choose the right form
| Meaning | Use | Decision |
|---|---|---|
| make a serious promise about a future action | swear to + base verb | Use the documented promise pattern. |
| use offensive language | swear / swear at + person, depending on structure | Treat this as a different sense, not a gerund complement. |
| use an -ing form directly after swear to name the promised action | swear doing | Do not treat this as the parallel promise complement. |
Quick tests
Promise-complement test
Does the following verb name an action the subject solemnly promises to perform?
If yes: Use “swear to + base verb.”
If no: If “swear” means use offensive language, use the structure required by that separate sense.
Caveat: The reviewed sources distinguish verb-complement patterns from the unrelated offensive-language sense; they do not license direct “swear doing” as the promise pattern.
Examples
She swore to keep the information confidential.
The infinitive names the action promised.
He swore to return the borrowed keys by Friday.
The promise sense takes “to + base verb.”
They swore to tell the truth.
The following infinitive expresses the promised action.
Further guidance
Decision
For the promise meaning, use “swear to do.”
Promise Pattern
Use swear + to-infinitive for a serious promise about a future action.
Sense Boundary
“Swearing” may refer to using rude or offensive language; that is a lexical sense of the verb, not the direct complement pattern “swear doing.”
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- swear — Oxford Advanced Learner’s Dictionary (opens in a new tab)Oxford Learner’s Dictionaries · Swear to do for a serious promise; separate intransitive swearing sense
- Verb patterns: verb + infinitive or verb + -ing? (opens in a new tab)Cambridge Dictionary · Verb-complement patterns, including verbs taking -ing, to-infinitive, or both with meaning differences