A tribit is a group of three bits that is transmitted, processed and interpreted like a single bit.
Tribits represent the eight (`2^3`) digital states 000, 001, 010, 011, 100, 101, 110 and 111 to which the valence of the octal system can be assigned. Tribits are used in quadrature amplitude modulation( QAM) and quadrature phase shift keying( QPSK) to increase the data rate. One example is V.27ter, another is PSK8 phase shift keying in EDGE.
If two bits are combined to form a group, this is referred to as a dibit; if four bits are combined, this is referred to as a quadbit, nibble or half- byte; if 8 bits are combined, this is referred to as a byte.