*2.2. LTS*

LTS is suitable for qualitative description of the decision-making problems, which can be defined as follows:

**Definition 1.** *Let S* = { *si*|*<sup>i</sup>* = 0, 1, ··· , 2*t* } *be a finite and totally ordered discrete linguistic term set, where si is a possible value for a linguistic variable, and t is a positive integer [33].*


In order to make the description of the given information more accurate, Xu [34] generalized the discrete linguistic term set *S* to the continuous linguistic term set *S* = { *si*|*<sup>i</sup>* ∈ [0, *τ*] } (*τ* > <sup>2</sup>*t*), where *si* ≤ *sj* if *i* ≤ *j*, and *τ* is a sufficiently large positive integer.
