A liquid crystal (LC) compound having generally required physical properties, low viscosity, proper optical anisotropy, proper dielectric anisotropy and good compatibility with other LC compounds is described. An LC composition including the compound and an LCD device including the composition are also described. The compound is expressed by formula (1a): wherein the ring A1 and the ring A2 are independently 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl or naphthalene-2,6-diyl, in which any hydrogen can be replaced by halogen; Z1, Z2 and Z3 are independently a single bond, —(CH2)2—, —(CH2)4—, —CH═CH—, —C≡C—, —CF2O—, —OCF2—, —COO— or —OCO—; Xa, Xb, Xc, Xd, Xe and Xf are independently hydrogen or fluorine; Y is —OCH2F, —OCHF2, —OCF3, —SCH2F, —SCHF2, —SCF3, —CH2F, —CHF2, —CF3, fluorine or chlorine; La and Lb are independently hydrogen or fluorine; and “l” and “m” are independently equal to 0 or 1.