Ligature is when two things are tied or stitched together, and it's also the thread or cord that's used to do the binding. If you hit your head and need stitches, you'll go to the emergency room for ligature.
Doctors and nurses are all well-trained in ligature (since they are always stiching people up), but they are not the only people familiar with ligature. When a robber ties up victims before robbing a store, the rope used to tie their hands is also a ligature, and when a musician connects two notes with a slur — singing or playing them as one syllable — that's a ligature too. The word comes from the Latin root ligatura, "a band," from ligare, "to bind."