What is a deductible vs. a copay vs. coinsurance? (Cross-line summary)

Different lines use these terms slightly differently:

• Deductible is the amount you pay out of pocket before insurance starts paying. Commercial property: per-claim deductible (e.g., $1,000 per loss). Commercial auto: per-accident deductible. Health insurance: annual deductible.
• Copay (mostly health insurance) is a fixed dollar amount per service after the deductible (e.g., $25 per primary care visit).
• Coinsurance is a percentage of cost shared between insurer and insured. In health, it's the percentage you pay after deductible (e.g., 20% of an MRI). In commercial property, coinsurance has a different meaning — it's a clause requiring you to insure property to at least 80% of replacement cost; underinsurance below the threshold reduces claim payouts proportionally.

For commercial coverage, deductibles are the main customer-facing sharing mechanism; coinsurance percentages and copays are mostly health-insurance terminology. See Batch 4 (Health) and Batch 2 (Property) for line-specific discussion.