Thread
noun
The kanji and the word are exactly the same. That means they share meanings as well.
いと
Since this word is made up of a single kanji it should use the kun'yomi reading (which is the reading you learned with the kanji).
糸は、たくさんあるよ。
There are many threads.
このタオル、糸が出てる。
Threads are sticking out of this towel.
この糸を二十センチに切って下さい。
Please cut this thread to 20 cm.