An airport is an aerodrome with extended facilities, mostly for commercial air transport. They usually consist of a landing area, which comprises an aerially accessible open space including at least one operationally active surface such as a runway for a plane to take off and to land or a helipad, and often includes adjacent utility buildings such as control towers, hangars and terminals, to maintain and monitor aircraft. Larger airports may have airport aprons, taxiway bridges, air traffic control centres, passenger facilities such as restaurants and lounges, and emergency services. In some countries, the US in particular, airports also typically have one or more fixed-base operators, serving general aviation.

Airport operations are extremely complex, with a complicated system of aircraft support services, passenger services, and aircraft control services contained within the operation. Thus airports can be major employers, as well as important hubs for tourism and other kinds of transit. Because they are sites of operation for heavy machinery, a number of regulations and safety measures have been implemented in airports, in order to reduce hazards. Additionally, airports have major local environmental impacts, as both large sources of air pollution, noise pollution and other environmental impacts, making them sites that acutely experience the environmental effects of aviation. Airports are also vulnerable infrastructure to extreme weather, climate change caused sea level rise and other disasters.

The terms aerodrome, airfield, and airstrip also refer to airports, and the terms heliport, seaplane base, and STOLport refer to airports dedicated exclusively to helicopters, seaplanes, and short take-off and landing aircraft.

The word aeroplane emerged in the 1870s, long before the Wright brothers succeeded in 1903. In colloquial use in certain environments, the terms airport and aerodrome are often interchanged. However, in general, the term airport may imply or confer a certain stature upon the aviation facility that other aerodromes may not have achieved. In some jurisdictions, airport is a legal term of art reserved exclusively for those aerodromes certified or licensed as airports by the relevant civil aviation authority after meeting specified certification criteria or regulatory requirements.

That is to say, all airports are aerodromes, but not all aerodromes are airports. In jurisdictions where there is no legal distinction between aerodrome and airport, which term to use in the name of an aerodrome may be a commercial decision. In US technical/legal usage, landing area is used instead of aerodrome, and airport means "a landing area used regularly by aircraft for receiving or discharging passengers or cargo".

Smaller or less-developed airfields, which represent the vast majority, often have a single runway shorter than 1,000 m (3,300 ft). Larger airports for airline flights generally have paved runways of 2,000 m (6,600 ft) or longer. Skyline Airport in Inkom, Idaho, has a runway that is only 122 m (400 ft) long.

As of 2009^[update], the CIA stated that there were approximately 44,000 "airports or airfields recognizable from the air" around the world, including 15,095 in the US, the US having the most in the world.

Many US airports still lease part or all of their facilities to outside firms, who operate functions such as retail management and parking. All US commercial airport runways are certified by the FAA under the Code of Federal Regulations Title 14 Part 139, "Certification of Commercial Service Airports".