One's share of a medical bill, maybe

• Fee for many a doctor's visit
• Doctor's visit fee for the insured
• Number at a doctor's office
• Amount owed by an insurance policy holder
• Patient's part of a bill
• Charge for visiting the doctor
• Insured patient's obligation
• Patient's portion
• Patient's share

Wiktionary Word definitions in Wiktionary
n. A copayment. vb. To jointly pay with another or others.