What Are the Principal Parts of Latin Verbs?

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

1. the present, active, indicative, first person, singular,
2. the present active infinitive,
3. the perfect, active, indicative, first person, singular, and
4. the past participle (or perfect passive participle), singular, masculine.

Taking as an example the first conjugation verb amo (love), you will see in the dictionary something like:

amo, -are, -avi, -atus.

This is an abbreviated form of the four principal parts:

amo, amare, amavi, amatus.

The four principal parts correspond with English forms:

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

• The present active indicative first 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 four 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 four 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 Four Principal Parts?

The four principal parts of the Latin verb give you all the information you need to conjugate the verb.

1. Not all first principal parts end in "-o". Some are in the third person, not first.
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 third 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 fourth principal part.

Sources and Further Reading

• Moreland, Floyd L., and Fleischer, Rita M. "Latin: An Intensive Course." Berkeley: University of California Press, 1977.
• Traupman, John C. "The Bantam New College Latin & English Dictionary." Third Edition. New York: Bantam Dell, 2007.