What Are the Principal Parts of Latin Verbs?

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When you learn a new Latin verb you generally learn an abbreviated form of the following 4 principal parts:

  1. the present, active, indicative, 1st person, singular,
  2. the present active infinitive,
  3. the perfect, active, indicative, 1st person, singular, and
  4. 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:

  1. I love (or I am loving) [present, active, 1st person, singular],
  2. To love [present active infinitive],
  3. I have loved (or I loved) [perfect, active, 1st person, singular],
  4. 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.

  1. Not all 1st principal parts end in "-o". Some are 3rd person, not 1st.
  2. The infinitive tells you which conjugation it is in. Drop the "-re" to locate the present stem.
  3. 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.
  4. 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.