rătĭuncula — Lewis & Short
rătĭuncula, ae, f.dim.ratio.
I 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.—
II A slight ground or reason:
leves,Cic. Tusc. 4, 19, 43:
huic incredibili sententiae ratiunculas suggerit,id. N. D. 3, 29, 73.—
2 In dialectics, a petty syllogism:
concludunt ratiunculas Stoici,Cic. Tusc. 2, 12, 29: humanis ratiunculis falsis contravenire conantur, Aug. Civ. Dei, 20, 1, 1.