A strait is a narrow, navigable channel of water that connects two larger navigable boies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not navigable, for example because it is too shallow, or because it contains an unnavigable reef or archipelago. The terms strait, channel, passage, sound, and firth can be synonymous and interchangeable, although each is sometimes differentiated with varying senses. Many straits are economically important. Straits can lie on important shipping routes, and wars have been fought for control of these straits. Numerous artificial channels, called canals, have been constructed to connect two bodies of water over land.