To provide a dialkyne compound used as a new, stable liquid crystal compound, having such a specific low optical anisotropy (Δn) and a negative or positive dielectric anisotropy (Δ) as to be suitably used as a liquid crystal medium, especially as a component for a TFT(thin film transistor) and STN(super-twisted nematic) display.

This dialkyne compound is expressed by the formula (I) [R1 and R2 are each H, F, a 1-15C substituted or unsubstituted alkyl or the like; X1 to X4 are each H or -C≡C-C≡C-R3 (R3 is H, CF3, a substituted or unsubstituted alkyl or the like); Q is -CH2- or -O-; Y1 and Y2 are each C or Si; A1 and A2 are each a trans-cyclohexylene which may be unsubstituted, or substituted by F or CN, or in which one, two or more nonadjacent CH2 groups are substituted by -O- and/or -S-, or the like; Z1 and Z2 are each a single bond, -CO-O-, -O-, -CF2-O-, -CH2-CH2- or the like; and n and m are each 0-3, provided that (m+n) is 1-3].