There are three important rules to remember:

(1) the// thematic vowel in fourth conjugation is -i-;

(2) the future tense sign in fourth conjugation is -e- and;

(3) the third-io conjugation resembles fourth conjugation more than third.

The formation of the present tense in fourth conjugation follows the same pattern as the other conjugations: a fourth-conjugation verb base is added a thematic vowel, in this case -i-, and onto that are appended personal endings. Those personal endings are the same we’ve seen in the other conjugations. Though the thematic vowel in fourth conjugation often shows up as a long -ī, nowhere is the long mark mandatory because it does not distinguish one form from another.

The translation of the present tense in fourth conjugation should pose no challenges. It follows the same pattern as the other conjugations:

The imperfect tense in fourth conjugation presents few surprises, too. It uses the tense marker - ba- just like the other conjugations, and to that adds personal endings. The only irregularity of any sort is that fourth conjugation uses a double thematic vowel, -ie-, in the imperfect, but that hardly counts as a surprise given how strong the presence of -i- is at the end of the base in fourth conjugation. Thus, the imperfect in fourth conjugation follows along the lines of

The fifth and final conjugation in Latin looks on the surface like it’s a blend of third- and fourth conjugation forms. Therefore, it’s called “third-io”. That’s because the first principal part ends -io, as if it were fourth-conjugation, but doesn’t have an -ire infinitive the way fourth-conjugation verbs do, but an -ere infinitive the way third-conjugation verbs do.

So it’s third because of its infinitive, and -io because of its first principal part. Here are three examples of third-conjugation -io verbs:

But in the third-io conjugation, the balance between third- and fourth-conjugation forms is nowhere near to even. There are far more forms that appear to be fourth-conjugation than third. Let’s look at “fugio”. You can see that it follows the same general pattern as the other conjugations: base plus thematic vowel plus personal endings:

The dominance of the -i- thematic vowel makes this conjugation look a lot like fourth, especially since the -i- rarely contracts into other forms. The translation of third-io conjugation verbs in the present tense follows exactly the same pattern as the other conjugations, for example: “I flee,” “I do flee,” “I am fleeing.”

The imperfect tense, where the -ba- tense sign, -ie- double thematic vowel like fourth conjugation, translates “was,” “used to,” “kept on.”

Now, the future. Maybe this will be exciting! Look at it: -e- future tense marker, -a- in the first person singular, no thematic vowel -i- lost, translates “will,” “will be.”