What device can be installed to feed a balanced antenna with an unbalanced transmission line?

A balun is an electrical device specifically designed to connect a BALanced antenna (like a dipole) to an UNbalanced transmission line (like coaxial cable). The term itself is a portmanteau of the words 'BALanced' and 'UNbalanced'. Using a balun prevents RF currents from flowing back down the outside of the coaxial shield, which can cause feedline radiation and interference in the radio shack. Distractors such as loading coils and wave traps are incorrect because they are used for changing an antenna's electrical length and blocking specific frequencies, respectively.