X setting (X sync) : is the setting that causes the flash to burst in synchronization with the shutter. For some manual cameras, the X synch speed refers to the maximum speed that the camera can synchronize with the flash.
Deoxyribonucleic Acid [DNA]
Deoxyribonucleic acid is a molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses. DNA and RNA are nucleic acids; alongside proteins, they compose the three major macromolecules essential for all known forms of life.