#3rd declension

Active

Let’s take the verb lego, legere, legi, lectus (to read) as we work through how to form the 3rd declension.

Now, for present active, you always use the first principle part for singular 1st person. Therefore, “I read” will be lego. 1st Person, Singular, and Active will always be the 1st principle part. Now, I will explain how to get the other forms down.

For present tense, these are the steps we’ll use.

Cut off the -ere in the infinitive.

Add i (except in 3rd person plural - there, use u)

Add active endings

Note that instead of cutting off the -re, you cut off the vowel plus the -re on the end of the 2PP. Also note that for only 3rd person plural will the vowel will be u instead of i in the second step. You’ll notice the u will be present here in the 3rd-io and 4th declensions as well! So, let us form the verb lego for 2nd person singular.

Legere

Legi

Legis

Legis is our 2nd Person Singular Present form of lego! This means “you read.” Now, let’s do 3rd person plural so we can see how to use the u.

Legere

Legu

Legunt

The 3rd person plural is legunt! This means “they read.” Now, here is a chart of all of the present active forms of lego:

For 3rd-io and 4th, we use mostly the same steps, although the 4th declension already has the i when you cut off the -re. However, for simplicity, we will use the same steps, as the 3rd and 4th declensions are grouped together in how they are formed.

The only difference is that on the 3rd person plural, we use iu instead of just u.

4th declension forming: audio, audire, audivi, auditus (to hear).

Let’s do 1st person plural active:

audire

audi

audimus

Therefore, the 1st person plural active form of audio is audimus. Here is a chart of audio:

Passive

The ending for 1st person singular in passive is -or. However, the 3rd-io and 4th declensions will have an -i in front of the -or. So lego will become legor, but audio will become audior.

To make the other passive persons and numbers, we use the same steps, but with passive endings:

Cut off the -vowel re

Add i/u/iu

Add passive endings

For an example, here’s facio, facere, feci, factus (to make or do) in 3rd person singular

facere

faci

facitur

And so the passive present singular 1st person is facitur.

Here’s the chart for facio in passive present: