A word clock or wordclock (sometimes sample clock, which can have a broader meaning) is a clock signal used to synchronise other devices, such as digital audio tape machines and compact disc players, which interconnect via digital audio. S/PDIF, AES/EBU, ADAT, and TDIF are some of the formats that use a word clock. Various audio over Ethernet systems use broadcast packets to distribute the word clock. The device which generates the word clock - usually with multiple output connectors - is the only master clock source for all the slave audio devices.
Word clock is so named because it clocks each sample. Samples are represented in data words.