Walking (also known as ambulation) is one of the main gaits of locomotion among legged animals, and is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults over the stiff limb or limbs with each step. This applies regardless of the number of limbs - even arthropods with six, eight or more limbs.

The word walk is descended from the Old English wealcan "to roll". In humans and other bipeds, walking is generally distinguished from running in that only one foot at a time leaves contact with the ground and there is a period of double-support. In contrast, running begins when both feet are off the ground with each step. This distinction has the status of a formal requirement in competitive walking events. For quadrupedal species, there are numerous gaits which may be termed walking or running, and distinctions based upon the presence or absence of a suspended phase or the number of feet in contact any time do not yield mechanically correct classification. The most effective method to distinguish walking from running is to measure the height of a person's center of mass using motion capture or a force plate at midstance. During walking, the center of mass reaches a maximum height at midstance while during running, it is at a minimum. Definitions based on the percent of the stride during which a foot is in contact with the ground (averaged across all feet) of greater than 50% contact corresponds well with identification of 'inverted pendulum' mechanics and are indicative of walking for animals with any number of limbs, although this definition is incomplete. Running humans and animals may have contact periods greater than 50% of a gait cycle when rounding corners, running uphill or carrying loads.

Aamir Hussain Khan (pronounced [ˈaːmɪr ˈxaːn]) (born 14 March 1965) is an Indian film actor, director and producer who has established himself as one of the leading actors of Hindi cinema.

Starting his career as a child actor in his uncle Nasir Hussain's film Yaadon Ki Baaraat (1973), Khan began his professional career eleven years later with Holi (1984) and had his first commercial success with Qayamat Se Qayamat Tak (1988). He received his first National Film Award as a Special Jury Award for his roles in the films Qayamat Se Qayamat Tak (1988) and Raakh (1989). After eight previous nominations during the 1980s and 1990s, Khan received his first Filmfare Award for Best Actor for his performance in the major grosser Raja Hindustani (1996) and later earned his second Best Actor award for his performance in the Academy Award-nominated Lagaan, which also marked the debut of his own production company.

Following a four-year break from acting, Khan made his comeback playing the title role in the historical Mangal Pandey: The Rising (2005), and later won a Filmfare Critics Award for Best Actor for his role in Rang De Basanti (2006). The following year, he made his directorial debut with Taare Zameen Par, for which he received a Filmfare Award for Best Director. This was followed by Ghajini (2008), which became the highest grossing film of that year, and 3 Idiots (2009), which became the highest-grossing Bollywood film of all-time, unadjusted for inflation. The Government of India honoured him with the Padma Shri in 2003 and the Padma Bhushan in 2010 for his contributions towards the arts.