The Complete Latin Infinitive 

The infinitive is a form that expresses the concept of a verb.  You already know the present active infinitive and the present infinitive of deponent verbs.  You learn them as the second principal part of each new verb.  Infinitives also occur in future and perfect tenses, and both active and passive voices.

Here is an overview of the infinitive in English before we learn the Latin forms.

Latin has infinitive forms in three tenses: present, perfect, and future.  The present and perfect infinitive forms, both active and passive, are used commonly.  The future active infinitive is common in Latin, although rare in English.  The future passive infinitive is rarely used in Latin.

Present Infinitives

Active forms:
The present active infinitive is simply the second principal part of active verbs.  We translate the active infinitive forms with “to” and the concept of the verb. E.g. amare - “to love.”

Passive forms:
To make the present passive infinitive, take the present active infinitive, remove the final -e and add -i, except in the third and third -io conjugation where the entire -ere infinitive ending is dropped before adding -i.  

amare - e  + i = amari   

scribere - ere + i = scribi 

We translate present passive infinitives as “to be X-ed.”  

The chart below shows how to form the present infinitive in all conjugations with a translation for each form.

Perfect Infinitives 

Active forms:
All perfect active forms are made from the third principal part (the first person singular perfect active indicative).  To form the perfect active infinitive, remove the -i from the third principal part and add -isse.

amav + -isse = amavisse

The perfect active infinitive is translated as “to have X-ed,” because, in English, we often use the helping verb “has/have” to indicate the perfect tense. 

The chart below shows how to form the perfect active infinitive in all conjugations with a translation for each form.

Passive forms:
All perfect passive forms are made from the fourth principal part. The infinitive is the perfect passive participle and esse (the infinitive of “to be”).  The two words remain separate.   The participle will still reflect the gender and number of the subject. (More on this in Indirect Statements below.)

amatum esse - to have been loved

The perfect passive infinitive is translated as “to have been X-ed.” 

The chart below shows how to form the perfect passive infinitive in all conjugations with a translation for each form.

Future Infinitives

The future active infinitive is used commonly in Latin in Indirect Statement, a construction for reporting speech which you will learn shortly.  The future passive infinitive is found only rarely.

Active forms:
All future active infinitives are made from the future active participle and esse (the infinitive of “to be”).  The two words remain separate.  

amaturum esse

The participle will still reflect the gender and number of the subject.  The future active infinitive is translated as “to be about to X.”

The chart below shows how to form the future active infinitive in all conjugations with a translation for each form.

Passive forms:
All future passive infinitive forms are unusual and rare.  They are made from the perfect passive participle in the neuter singular and iri (the present passive infinitive of eo “to go”).  The two words remain separate.  The participle never changes its ending. 

amatum iri - to be about to be loved

The future passive infinitive is translated as “to be about to be X-ed.” 

The chart below shows how to form the future passive infinitive in all conjugations with a translation for each form.

Overview of All Six Infinitives for Each Conjugation

First Conjugation

Second Conjugation

Third Conjugation

Third -io Conjugation

Fourth Conjugation

What is an Indirect Statement?

In Unit I, you learned how to use infinitives as Complementary Infinitives, to complete the meaning of other verbs.  Now you will learn how to use infinitives in an important Latin construction: Indirect Statement.  

Indirect statements are used to report statements that are said, thought, or felt.  Let’s begin by considering some examples in English.

Direct statement: Aelia says, “The penalties are bad”
Indirect statement: Aelia says that the penalties are bad.

Direct statement: Hilarianus thought, “Aelia loves philosophy.”
Indirect statement: Hilarianus thought that Aelia loved philosophy.

In English, there is not much change between a direct and indirect statement.  In Latin, there will be a complete change in construction.

Sentences that use indirect statement in Latin will have main verbs of sensation, or “verbs of the head.”  These can include verbs of thinking, hearing, seeing, feeling, knowing, saying, denying, and many others.  The content of what is thought, heard, seen, or felt must be reported in Latin with an accusative-infinitive construction.   

Let’s return to our examples from above.  

Aelia says, “The penalties are bad.”
Direct statement: Aelia dicit, “Poenae sunt malae.”

The main clause “Aelia says” does not change. To report what Aelia says indirectly, rather than quote her directly, we use an indirect statement.  In Latin, this idea is written so that the subject of the indirect statement is in the accusative and the verb is in the infinitive.  Note in the Latin below that malas, as the predicate adjective referring back to poenas, is in the accusative case.

Aelia says that the penalties are bad.
Indirect statement: Aelia dicit poenas esse malas.

In the second example from above, the main verb is in the imperfect tense.

Hilarianus thought that Aelia loved philosophy.

The main clause is “Hilarianus thought.” What he knew is reported as an indirect statement with a subject accusative and an infinitive verb.  Here is the sentence in Latin:

Hilarianus cogitabat Aeliam philosophiam amare.

Notice that Latin does not use a word for “that,” a word which often appears in English indirect statements. 

Tenses of Infinitive and Relative Time

In indirect statements, the tense of the reported action shows time relative to the main verb.  Let’s return to the example above:

Hilarianus cogitabat Aeliam philosophiam amare.
Hilarianus thought that Aelia loved philosophy.

The indirect statement uses a present infinitive to shows that the action of the main verb and the action of indirect statement are both happening at the same time.

Here is a summary of how each infinitive tense denotes relative time in indirect statement:

Present Infinitive: action occurs at the same time as the action of the main verb

Perfect Infinitive: action occurs prior to, or before the action of the main verb

Future Infinitive: action occurs following, or after the action of the main verb

Here are our examples once again. Notice how changing the verb tense in the indirect statement changes the meaning.

Present Infinitive: Aelia cogitat poenas esse malas.
Aelia thinks that the penalties are bad. (at the same time)

Perfect Infinitive: Aelia cogitat poenas fuisse malas.
Aelia thinks that the penalties were bad. (previously)

Future Infinitive: Aelia cogitat poenas futuras esse malas.
Aelia thinks that the penalties are going to be bad. (in the future)

In our second set of examples, the main verb is imperfect. Notice how our translation of the infinitive shifts depending on the tense of the main verb.

Present Infinitive: Hilarianus cogitabat Aeliam philosophiam amare.
Hilarianus thought Aelia loved philosophy. (same time)

Perfect Infinitive: Hilarianus cogitabat Aeliam philosophiam amavisse.
Hilarianus thought Aelia had loved philosophy. (previously)

Future Infinitive: Hilarianus cogitabat Aeliam philosophiam amaturam esse.
Hilarianus thought Aelia was going to love philosophy. (in the future)

Notice the future active infinitive in the last example: amaturam esse.  It has the ending -am to agree with the accusative subject Aeliam.  When using perfect passive and future active infinitives, which are made up of a participle and esse, you must make the participle agree in gender and number with the accusative subject.  

Look at these examples.

Aelia believes that Apollonius will read her letter.
Aelia credit Apollonium litteram suam lecturum esse.

In this example the future active infinitive, lecturum esse, agrees with Apollonium, the masculine singular accusative subject of the indirect statement.

Hilarianus thinks that the temples were revered by the citizens.
Hilarianus putat templa a civibus culta esse.

In this example the perfect passive infinitive, culta esse, agrees with templa, the neuter plural accusative subject of the indirect statement.

Fourth Declension

Nouns of theFourth Declension appear in all three genders.  Masculine nouns are the most common in the fourth declension, but there are some feminine fourth declension nouns.  The most common is manus, manūs (f.) - hand.  The noun domus uses both 2nd and 4th declension endings and it is also feminine.  There are relatively few neuter fourth declension nouns.  The dominant letter in all genders is -u.

Like the third declension, masculine and feminine fourth declension nouns share the same endings, while the neuter forms have slight differences.  You can identify a fourth declension noun by the genitive ending -ūs. 

 The fourth declension masculine and feminine genders use the following endings:

To decline a masculine or feminine noun of the fourth declension, take the stem (found by dropping the ending from the genitive form) and add the endings above to it.  Here is the declension pattern for metus, metūs (m.) - fear, dread.

Fourth declension nouns that are Neuter have slightly different endings.  There are only four regularly occurring fourth declension neuter nouns.  The most common are cornu, cornūs (n.) - horn, and genu, genūs (n.) - knee.  The genitive singular ends in -ūs. Notice that all the other singular forms end in -u.

To decline a neuter noun in the fourth declension, take the stem (found by dropping the ending from the genitive form) and add the endings above to it:

Notice that the singular forms have the same ending (-u), except for the genitive.  All neuter nouns, regardless of declension, follow the “neuter rule,” meaning that they will have the same ending in the nominative and accusative singular, and in the nominative and accusative plural.

Fifth Declension

Nouns of the Fifth Declension are feminine.  There are two exceptions to this rule: 1) dies, diei (m./f.) - “day” is usually masculine, but can be feminine in the singular when referring to time in general.  The compound meridies, meridiei (m.) - “midday” is masculine.  You can identify a fifth declension noun by the nominative ending in -es and genitive in -ei.  

The fifth declension nouns use the following endings:

When declining a noun of the fifth declension, we take the stem (found by dropping the ending -ei from the genitive form) and add the endings above to it.  Here is the declension pattern for res, reī (f.) - a thing, matter. 

Degrees of Adjectives

In Unit 2, you learned how Latin adjectives modify nouns and how to decline the two types of adjectives, first and second declension adjectives and third declension adjectives.  At that time, you learned the positive degree of the adjectives which attribute a simple quality to a noun, for example, vera amica, or “true friend.”

Latin adjectives, like English adjectives, have three degrees that allow you to express the intensity of an adjective and to make comparisons between nouns.

Positive: Attributes a simple quality to a noun, e.g. “true friend.”

Comparative: Attributes a quality to a noun that makes a comparison and shows that the noun has more of a quality than one other noun (either explicit or implied), e.g. “truer friend,” “more true friend,” or “rather true friend.”

Superlative: Attributes a quality to a noun that shows the noun has the most of this quality, e.g. “truest friend” or “most true friend.”

Like positive degree adjectives, comparative and superlative degree adjectives agree with the nouns they modify in gender, number, and case.  As you have already learned how to make positive degree adjectives in Unit 2, we will focus here on the forms of the comparative and superlative degrees.

Forming Comparative Adjectives

All comparative adjectives use third declension endings, no matter what their original declension pattern. There is one set of endings for masculine and feminine adjectives and another set of endings for neuter forms.  

To make the masculine and feminine comparative forms of any regular adjective, use the adjective stem and add the endings below: 

Notice how the letters -ior- are part of every form.  Like the ending -er in comparative forms in English, these letters will help you recognize comparative forms.  Comparative adjectives are not i-stems and use -e for the ablative singular form.

To make the neuter comparative forms of any regular adjective, use the adjective stem and add the endings below: 

Notice how the endings only differ from masculine and feminine forms in the nominative and accusative singular, and in the nominative and accusative plural.  All neuter adjectives, regardless of declension, follow the “neuter rule,” meaning that they will have the same ending in the nominative and accusative singular, and in the nominative and accusative plural.

Here are the full declensions of two adjectives that you already know from Unit 3 and Unit 4 in the comparative degree: laetus, -a, -um is a first and second declension adjective; gravis, grave is a third declension adjective.  Both will use third declension endings in the comparative degree.

Comparative forms of laetus, -a, -um 

Comparative forms of gravis, grave

Making Comparisons with Comparative Adjectives

Comparative adjectives can be used two ways:

1.  to modify a noun in an implied comparison.  

Aelia laetior puella est.
“Aelia is a happier girl.” or “Aelia is a rather happy girl” (understood: than other girls)

Hilarianus graviores res gerebat.
“Hilarianus was managing more serious matters.” Or, “Hilarianus was managing rather serious matters.” (understood: than his other concerns)

2.  to make direct comparisons between two nouns in respect to the same quality.  

Aelia is a happier girl than her friend.

Hilarianus was managing matters more serious than gladiatorial shows.

There are two ways to make direct comparisons in Latin:

1.  Modify the primary noun with a comparative adjective, add quam (“than”) and the noun to which it is compared in the same case as the primary noun.  Here are our examples from above in Latin:

Aelia laetior quam amica est.
 “Aelia is a happier girl than her friend.”
        (Aelia and amica are both in the nominative.)

Hilarianus res graviores quam munera gerebat.
“Hilarianus was managing matters more serious than gladiatorial shows.”
        (Res and munera are both in the accusative.)

2. Modify the primary noun with a comparative adjective and follow it with the ablative form of the noun to which it is compared. Do not use quam.  Here are our examples from above in Latin:

Aelia laetior amicā est.
“Aelia is a happier girl than her friend.”
        (Aelia is in the nominative but amicā is in the ablative.)

Hilarianus res graviores muneribus cogitabat.
“Hilarianus was managing matters more serious than gladiatorial shows.”
        (Res is in the accusative but muneribus is in the ablative.)

You will see both ways of making comparisons when you read Latin.  The second way, using the ablative of comparison without quam, can be harder to recognize.

Forming Superlative Adjectives

All superlative adjectives use first and second declension endings, no matter their original declension pattern. There are separate endings for the masculine, feminine, and neuter forms.  

To make comparative forms of any regular adjective, use the adjective stem, add “-issim-” and first and second declension adjective endings below: 

Notice how the letters -issim- are part of every form.  These letters will help you recognize superlative forms, like the ending “-est” in many superlative adjective forms in English.  

Here are the full declensions of two adjectives that you already know from Unit 3 and Unit 4 in the superlative degree: laetus, -a, -um is a first and second declension adjective; gravis, grave is a third declension adjective.  Both will use first and second endings in the superlative.

Superlatives forms of laetus, -a, -um 

Superlative forms of gravis, grave 

Two exceptions to the rules for forming superlative adjectives: -limus and -rimus adjectives

1.  If the adjective stem ends in -l, you add “-lim-” and first and second declension endings.  Look at the superlative forms of a new vocabulary word facilis, -e “easy” (stem = facil-).

facillimus, -a, -um “easiest”

2. If the masculine nominative singular ends in -er, you add "-rim-" and first and second declension endings.  Look at the superlative forms of miser, misera, miserum  “miserable” (stem = miser-).

miserrimus, -a, -um “most miserable”

Two Ways to Use the Superlative Adjective

The superlative adjective is most often used modifying a noun to say that the noun has the greatest quality of an adjective, for example:

Aelia laetissima est.
Aelia is the happiest.

Hilarianus res gravissimas gerebat.
Hilarianus was managing the most serious matters.

You can also use the superlative adjective to express that something has the highest possible degree of an adjective.  To do this, add “quam” to your sentence before the superlative adjective. 

Aelia quam laetissima est.
Aelia is as happy as possible.

Hilarianus res quam gravissimas gerebat.
Hilarianus was managing matters as serious as possible.

Irregular Comparative and Superlative Adjectives

Just as in English, some of the most common adjectives in Latin have irregular comparative and superlative forms.  Often they change stems in the comparative and superlative degrees just like “bad,” “worse,” and “worst” in English.  Because these stem changes cannot be predicted from the stem of the positive degree, it is important to learn these comparative and superlative forms. They have been included as vocabulary in this unit.

*plus (gen. pluris) is neuter singular and functions as a noun. There are no singular masculine and feminine forms.  For example, to say “more water” in Latin, you would say plus aquae or “more of water.”  There are plural forms for all three genders. 

Comparison of Adjectives Lacking a Positive Form

Some adjectives that have comparative and superlative forms lack a positive degree form, Usually they are derived from propositions.  The more common forms have been included in your Verba.

Changing Adjectives to Adverbs (Review)

In Unit 4, you learned how to change adjectives into adverbs.  In order to form an adverb from a 1st and 2nd declension adjective, you add the ending -e.  In order to form an adverb from a 3rd declension adjective, you add the ending  -iter.

1st and 2nd Declension Adjective

certus, -a, -um      certe
certain                    certainly

3rd Declension Adjective

dulcis, -e                dulciter
sweet                      sweetly

Comparative and Superlative Adverbs

Just like adjectives, adverbs also have degrees, which means there are comparative and superlative adverbs.  Also like adjectives, in the comparative and superlative degrees the endings stay the same across declensions. 

The ending for the comparative adverb is -ius (this is the same ending for the comparative adjective in the neuter, singular, nominative/accusative).  The comparative adverb in English is translated as “more ______ly.”

certus, -a, -um          certe                certius
certain                    certainly             more certainly

dulcis, -e                dulciter               dulcius
sweet                     sweetly           more sweetly

The ending for the superlative adverb is -issime, which includes the typical -issim- included with superlative adjectives.  The superlative adverb in English is translated as “most _______ly.”

certus, -a, -um         certe              certius                    certissime
certain                   certainly          more certainly        most certainly

dulcis, -e               dulciter              dulcius                      dulcissime
sweet                     sweetly         more sweetly               most sweetly

similis, -e             similiter           similius                      simillime
similar                  similarly        more similarly           most similarly

miser, -a, -um     misere            miserius                     miserrime
wretched            wretchedly       more wretchedly       most wretchedly

These endings can also be used for adverbs that were not derived from adjectives.  

diu                              diutius                          diutissime
for a long time       for a longer time            for the longest time

saepe                         saepius                           saepissime
often                      more often                        most often