“Swam” and “swum” are different forms of the irregular verb “swim.” “Swam” is the simple past, while “swum” is the past participle used in perfect constructions and, where applicable, passive constructions.
ReviewedEvidence1 sourceSectionEnglish Usage
Quick answer
Use “swam” for the simple past and “swum” as the past participle, especially after have/has/had.
Key details
Confusion Familyirregular verb forms
Rule Familyverb forms
Termsswam, swum
Verb Formsswim, swam, swum
Choose the right form
Decision table for Swam vs. Swum
Sentence need
Use
Example
simple past
swam
They swam yesterday.
past participle after have/has/had
swum
They have swum before.
Further guidance
Core difference
“Swam” is the simple-past form of “swim”; “swum” is the past participle used with auxiliaries such as have, has, or had and in passive constructions when the verb permits them.
Fast Test
If have, has, or had directly governs the form of “swim,” choose “swum.” For a standalone finite past-tense verb, choose “swam.”
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.
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