Price war is a term used in the economic sector to indicate a state of intense competitive rivalry accompanied by a multi-lateral series of price reductions. One competitor will lower its price, then others will lower their prices to match. If one of them reduces their price again, a new round of reductions starts. In the short term, price wars are good for consumers, who can take advantage of lower prices. Often they are not good for the companies involved because the lower prices reduce profit margins and can threaten their survival.

In the medium to long term, price wars can be good for the dominant firms in the industry. Typically, the smaller, more marginal, firms cannot compete and must close. The remaining firms absorb the market share of those that have closed. The real losers then, are the marginal firms and their investors. In the long term, the consumer may lose too. With fewer firms in the industry, prices tend to increase, sometimes higher than before the price war started.

The main reasons that price wars occur are:

A fare is the fee paid by a passenger allowing them to make use of a public transport system: rail, bus, taxi, etc. In the case of air transport, the term airfare is often used.

The fare paid is a contribution to the operational costs of the transport system involved, either partial (as is frequently the case with publicly supported systems) or total. The portion of operating costs covered by fares - the farebox recovery ratio - typically varies from 30%-60% in N America and Europe, with some rail systems in Asia over 100%.

The rules regarding how and when fares are to be paid and for how long they remain valid are many and varied. Rail and bus systems usually require the payment of fares on or before boarding. In the case of taxis and other vehicles for hire, payment is normally made at the end of the ride.

Some systems allow free transfers: that is to say that a single payment permits travel within a particular geographical zone or time period. Such an arrangement is helpful for people who need to transfer from one route to another in order to reach their destination. Sometimes transfers are valid in one direction only, requiring a new fare to be paid for the return trip.

War is an organized, armed, and often a prolonged conflict that is carried on between states, nations, or other parties typified by extreme aggression, social disruption, and usually high mortality. War should be understood as an actual, intentional and widespread armed conflict between political communities, and therefore is defined as a form of political violence. The set of techniques used by a group to carry out war is known as warfare. An absence of war (and other violence) is usually called peace.

In 2003, Nobel Laureate Richard E. Smalley identified war as the sixth (of ten) biggest problems facing the society of mankind for the next fifty years. In the 1832 treatise On War, Prussian military general and theoretician Carl von Clausewitz defined war as follows: "War is thus an act of force to compel our enemy to do our will."

While some scholars see warfare as an inescapable and integral aspect of human culture, others argue that it is only inevitable under certain socio-cultural or ecological circumstances. Some scholars argue that the practice of war is not linked to any single type of political organization or society. Rather, as discussed by John Keegan in his History of Warfare, war is a universal phenomenon whose form and scope is defined by the society that wages it. Another argument suggests that since there are human societies in which warfare does not exist, humans may not be naturally disposed for warfare, which emerges under particular circumstances. The ever changing technologies and potentials of war extend along a historical continuum. At the one end lies the endemic warfare of the Paleolithic^{[citation needed]} with its stones and clubs, and the naturally limited loss of life associated with the use of such weapons. Found at the other end of this continuum is nuclear warfare, along with the recently developed possible outcome of its use, namely the potential risk of the complete extinction of the human species.