Generally, string is a thin piece of fiber which is used to tie, bind, or hang other objects. String can be made from a variety of fibres. The term has more specific meanings within certain academic disciplines.
Biology
In biology, a string is a chain of biochemicals.
Mathematics and computer science
In various branches of mathematics and computer science, strings are sequences of various simple objects (symbols, tokens, characters, etc.), used in many contexts. See String (computer science).
Music
A string is a vibrating cord of metal, nylon, gut or other substance such as wound hair that vibrates to produce a tone in a variety of musical instruments. Strings can also refer to the section of an orchestra or band consisting in stringed instruments. See string instrument.
Physics
In theoretical physics, a string is the basic object of study in string theory. In string theory, strings replace the notion of elementary particles in quantum field theory. See also: open string, closed string.