The stabbing happened around 12:35 p.m. on the CTA Blue Line in the 3600 block of West Addison Street, Chicago police said.
The victim, a 29-year-old man, was in an altercation with an unknown offender who stabbed him with a knife on his shoulder and the back of his head, police said.
The man was taken to a hospital in good condition, CPD said. The offender was taken into custody but has not yet been identified.
No further information was immediately available.
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