The class of context-free languages which can be represented by grammars where each word in the language has exactly one leftmost derivation.
Strictly contains Deterministic CFL. Strictly contained in CFL.
Contained in LOGCFL.
Strictly contains DCFL [Bra77] and indeed UCFL.
The class of languages accepted by deterministic pushdown automata.
Defined in [GG66], where it was also shown that DCFL is strictly contained in CFL, contained in UCFL, and strictly contains REG. The inclusion in UCFL is also strict.