MDI

• Media Delivery Index, a metric used in IPTV networks
• Medium-dependent interface (MDI) and medium-dependent interface crossover (MDI-X), types of Ethernet port connections
• Microsoft Document Imaging Format, a proprietary file format
• Mission Data Interface, an interface developed by NUWC Keyport
• Multiple-document interface, a type of software application interface
• Multi-Draw Indirect, a rendering technique

• Major Depression Inventory, a self-report mood inventory developed by the World Health Organization
• Metered-dose inhaler, a device that helps deliver a specific amount of medication to the lungs
• Multiple drug intake, an unnatural cause of death
• Multiple Daily Injections, a technique of intensive insulinotherapy
• Mental Development Index, a measure of the cognitive abilities of infants and part of the Bayley Scales of Infant Development

• Management Development Institute, a business school in Gurgaon, India
• Merchants Distributors, Inc., a wholesale grocery store distributor based in Hickory, North Carolina
• Movement for Democracy and Independence, a former political party in the Central African Republic
• Motor Development International, a compressed air car maker

• Mount Desert Island, an island off the coast of the U.S. state of Maine
• Methylene diphenyl diisocyanate, a chemical
• Michelson Doppler Imager, an instrument on board the SOHO spacecraft
• 1501, in Roman numerals
• Medically determinable impairment, a factor in establishing disability under Social Security Disability Insurance and Supplemental Security Income

• MD1 Ministry of Defence 1, a British weapon research and development organisation of the Second World War

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