The amount you pay for health care services before your health insurance begins to pay anything to your provider.  You pay all costs/chargers until your deductible is "satisfied".

A set dollar amount determined by your insurance that must be paid to your physician, hospital or pharmacy every time a service is utilized.  (Ophthalmology is a "specialty" and may have a different copay than your PCP).

Your share of the costs of a health care service.  It's usually figured as a percentage of the amount your insurance allows to be charged for services.  You start paying coinsurance after you've paid your plan's deductible.