Figure 1. Schematics of local director arrangements in nematics.

(a) Nematic N phase, uniaxial alignment, θ₀=0, (b) N_tb, with oblique helicoid 0<θ₀<π/2 and (c) chiral nematic N* phase, right helicoid, θ₀<π/2 (the twist is right-handed or left-handed, depending on molecular chirality.