- the present, active, indicative, 1st person, singular,
- the present active infinitive,
- the perfect, active, indicative, 1st person, singular, and
- the past participle (or perfect passive participle), singular, masculine.
Taking as an example the 1st conjugation verb amo (love), you will see in the dictionary something like:
amo, -are, -avi, -atus.This is an abbreviated form of the 4 principal parts:
amo, amare, amavi, amatus.
The 4 principal parts correspond with English forms:
- I love (or I am loving) [present, active, 1st person, singular],
- To love [present active infinitive],
- I have loved (or I loved) [perfect, active, 1st person, singular],
- Loved [past participle].
In English, however, you usually just learn something referred to as the verb, as in "love". That doesn't mean English lacks principal parts -- just that we tend to ignore them and if we learn them, we don't have to learn 4:
- The present active indicative 1st person singular of love, is love,
- the simple past tense and the past participle = loved.
If you learn the verb is "love" or "to love" you know to add the "-d" for the past. This makes it seem onerous to have to learn 4 forms for each Latin verb; however, even in English we sometimes face a similar challenge. It all depends on whether we're dealing with what is called a strong verb or a weak one.
Having 4 principal parts not so different from English if you
- insert the infinitive ("to" + the verb) in the list of principal parts, and
- look at a strong verb like "ring" rather than a weak verb like "love".
A strong verb in English changes the vowel to change the tense. I --> A --> U in the following example:
- Ring is the present,
- To ring is the present infinitive,
- Rang is the past, and
- Rung is the past participle.
A weak verb (like love) doesn't change the vowel.
Why Should You Notice the 4 Principal Parts?
The 4 principal parts of the Latin verb give you all the information you need to conjugate the verb.
- Not all 1st principal parts end in "-o". Some are 3rd person, not 1st.
- The infinitive tells you which conjugation it is in. Drop the "-re" to locate the present stem.
- The perfect form is often unpredictable, although usually you just drop the terminal "-i" to find the perfect stem. Deponent and semi-deponent verbs only have 3 principal parts: The perfect form doesn't end in "-i". Conor, -ari, -atus sum is a deponent verb. The 3rd principal part is the perfect.
- Some verbs can't be made passive, and some verbs have the active future participle in place of the past participle for the 4th principal part.