The present tense

Latin sorted its verbs into four conjugations by the vowel before the infinitive ending: -ĀRE (CANTĀRE 'to sing'), -ĒRE with a long, stressed e (VIDĒRE 'to see'), -ERE with a short, unstressed e (VENDERE 'to sell'), and -ĪRE (DORMĪRE 'to sleep'). The sisters inherited all four and then tidied them up, each in its own way.

Spanish merged the two e-classes into a single -er, leaving three: -ar, -er, -ir; Portuguese did the same. Italian kept the Latin difference as a difference of stress: vedere is stressed on the ending, vendere on the stem. Romanian kept it too, as two separate conjugations: vedea (veDEa) against vinde (VINde). Catalan likewise keeps a stressed -er (saber, voler) apart from an unstressed -re (vendre, perdre), though VIDĒRE itself moved over to give veure. French regrouped by behavior rather than by vowel: the 1st group (-er, from -ĀRE) is huge and regular; the 2nd group is the -ir verbs that add -iss- (finir, choisir); the 3rd group holds everything else (vendre, voir, dormir, partir).

CANTŌ, CANTĀS, CANTAT

Spanish and Portuguese are the most conservative here: they kept the final -s of the 'you' form and the -mos of 'we'. In Brazil, though, tu and vós give way to você / vocês with the 3rd-person verb (você canta, vocês cantam). Italian lost final -s and uses -i for 'you' in every class (canti, vedi, dormi), and its 'we' ending -iamo is shared by all verbs, a Tuscan ending taken over from the old subjunctive. Romanian sides with Italian: no final -s, -i for 'you' (cânți), and in this class 'they sing' sounds just like 'he sings' (cântă). Catalan keeps the -s (cantes) but wore 'we' and 'you all' down to -m and -u (cantem, canteu); its 'I' ending -o is a late arrival, since medieval Catalan said simply jo cant. French spelling still shows the Latin endings, but speech has worn them away: chante, chantes and chantent all sound the same, ʃɑ̃t.