Lewis & Short

symmē̆trĭa, ae, f., = συμμετρία, proportion, symmetry (cf. congruentia), Vitr. 1, 2; Plin. 34, 8, 19, §§ 58 and 65; 35, 10, 36, § 67.
Plur., Vitr. 1, 3 fin.