Nonius Marcellus, Compendium of Doctrine, Vol. II

original: "ego pérvicaciam áio et ea me utí volo. / haec fórtis sequitur, íllam indocti póssident; / tu addís quod vitióst, démis quod laudí datur."
I say it is stubbornness and I want to use it myself. This [stubbornness] follows the brave, the unlearned possess that [obstinacy]; you add what is a vice, you take away what is given to praise.

SENSVS senses/perceptions and SENSA things sensed/thoughts are separated in this way: for sensus are those who perceive, sensa are the things that are perceived. Cicero in On the Orator: "And because we can express thoughts sensa in speaking..." for first it is manifest that we are wise when there is an incitement or a sense sensus.

IVVENTVS youth (the collective body) and IVVENTA youth (the age) and IVVENTAS youth (the impulse) differ in this: iuventus refers to the young people, iuventa to the age itself, iuventas to what the Greeks call an impulse hormen or passion pathos. Vergil, Georgics book II:

original: "et patiens operis parvoque adsueta iuventus."
and a youth accustomed to little work and patient of labor.

Sallust in the War of Catiline: "and there he exercised his youth iuventutem." — The same in Catiline: "I know there were some who thought that the youth iuventutem that frequented the house of Catiline..." Vergil, Georgics book III:

original: "interea, superat gregibus cum laeta iuventas, / solve mares."
meanwhile, when a joyful youth iuventas here: reproductive vigor/impulse abounds in the herds, release the males.