Investigations on an algebraic structure of linguistic truth values in decision making and social science applications still lack a formalism for development of strict linguistic truth-valued logic system and its approximate reasoning scheme in practice. To attain this goal we characterize and construct the structure of linguistic value sets in natural language by a lattice-valued algebra structure - lattice implication algebra (LIA), where Łukasiewicz implication algebra, as a special case of LIA, plays a substantial role. By using Łukasiewicz logic's axiomatizability in terms of Pavelka type fuzzy logic, we propose a new axiomatizable linguistic truth-valued logic system based on LIA to place an important foundation for further establishi...