Unidirectional refers to something that moves or operates in one direction only. This concept can be applied in various fields, such as physics, where a unidirectional force acts in a single direction, or in communication systems, where information flows from one source to a receiver without feedback. In technology, unidirectional data transmission means that data travels from a sender to a receiver without the ability for the receiver to send data back. This is common in systems like broadcast television or radio, where signals are sent out to many receivers, but those receivers cannot respond to the source.