ratiuncula, ae, f. dim. ratio. A small reckoning, a little account: subduxi ratiunculam, Quantum aeris mihi sit, quantumque alieni siet, Plaut. Curc. 3, 1; id. Capt. 1, 2, 89; Ter. Phorm. 1, 1, 2.

— A slight ground or reason: leves, Cic. Tusc. 4, 19, 43: huic incredibili sententiae ratiunculas suggerit, id. N. D. 3, 29, 73.

— In dialectics, a petty syllogism: concludunt ratiunculas Stoici, Cic. Tusc. 2, 12, 29: humanis ratiunculis falsis contravenire conantur, Aug. Civ. Dei, 20, 1, 1.