Lewis & Short

per-tĕnŭis, e, adj., very thin, very small or fine.

  1. I. Lit.: sabulum pertenue, Plin. 18, 6, 7, § 34.
  2. II. Trop., very slight or slender, very weak: spes salutis, Cic. Fam. 14, 3, 2: discrimen, id. Agr. 2, 32, 87: suspicio, id. Clu. 60, 168: argumentum, id. Verr. 1, 6, 17: ars, id. de Or. 1, 23, 107.