Medicare glossary

Plain-language definitions of common Medicare terms. This is general information, not personalized advice, and plan details change every year. For all of your options, contact Medicare.gov or 1-800-MEDICARE.

Original Medicare: Original Medicare is the federal program combining Part A (hospital) and Part B (medical) coverage, with no networks and no built-in drug coverage.
Medicare Part A: Medicare Part A is hospital insurance covering inpatient stays, skilled nursing, hospice, and some home health care.
Medicare Part B: Medicare Part B is medical insurance covering doctor visits, outpatient care, preventive services, and some equipment, for a monthly premium.
Medicare Advantage / Part C: Medicare Advantage (Part C) is a private-plan alternative to Original Medicare that bundles Part A, Part B, and usually drug coverage.
Medicare Part D: Medicare Part D is prescription drug coverage from private insurers, available as a standalone plan or built into many Medicare Advantage plans.
Medigap: Medigap (Medicare Supplement Insurance) is private coverage that helps pay costs Original Medicare leaves to you, standardized by plan letter.
Special Needs Plan: A Special Needs Plan is a Medicare Advantage plan tailored to people who are dual eligible, institutionalized, or have certain chronic conditions.
Dual Eligible Special Needs Plan: A Dual Eligible Special Needs Plan (D-SNP) is a Medicare Advantage plan for people who have both Medicare and Medicaid.
Initial Enrollment Period: The Initial Enrollment Period is the seven-month window around your 65th birthday when you first sign up for Medicare.
Annual Enrollment Period: The Annual Enrollment Period (October 15–December 7) is when you can join, switch, or drop a Medicare Advantage or Part D plan.
Open Enrollment Period: The Medicare Advantage Open Enrollment Period (January 1–March 31) lets current Advantage members switch plans or return to Original Medicare.
Special Enrollment Period: A Special Enrollment Period lets you change Medicare coverage outside the usual windows after qualifying life events, such as losing employer coverage.
Formulary: A formulary is the list of prescription drugs a Part D or Medicare Advantage plan covers, organized into cost tiers.
Premium: A premium is the amount, usually monthly, you pay to keep an insurance plan, separate from what you pay when you use care.
Deductible: A deductible is the amount you pay for covered care before your plan starts paying its share.
Copayment: A copayment is a fixed dollar amount you pay for a covered service, such as a doctor visit or prescription.
Coinsurance: Coinsurance is the percentage of a covered cost you pay, with your plan paying the remaining share.
Network: A network is the set of providers a plan contracts with; in-network care usually costs less, and Original Medicare has no network.
Extra Help / Low-Income Subsidy: Extra Help (Low-Income Subsidy) is a federal program that lowers Medicare Part D drug costs for people with limited income and resources.
Scope of Appointment: A Scope of Appointment is a required form documenting which plan types you agree to discuss with an agent before a meeting.
Guaranteed Issue Rights: Guaranteed issue rights are situations where a company must sell you a Medigap policy regardless of health, set by federal and state rules.
Medicare Broker vs. Agent: Medicare broker and agent are largely interchangeable terms for licensed professionals who help you compare and enroll in plans.
Non-Government Medicare Directory: A non-government Medicare directory is a private website listing agents or plan info, not affiliated with or endorsed by Medicare.