String was a thin version of cord or rope, braided and made in a similar manner.
A man from Canton, Ohio once rolled a ball of string over six meters in diameter. (ENT: "The Andorian Incident")
In the year 2000, Indiana was the home of the world's largest ball of string. Shannon O'Donnel saw it in December of that year. (VOY: "11:59")
When communications was down on Deep Space 9 in 2373, Jadzia Dax jokingly asked whether they should substitute "cups and a long string". (DS9: "For the Uniform")