The Four Conjugations

171. Verbs are classed in Four Regular Conjugations, distinguished by the stem vowel which appears before -re in the Present Infinitive Active.

172. The Principal Parts of a verb, showing the three stems which determine its conjugation throughout, are—

1. The Present Indicative ( amō ), showing the Present Stem.
2. The Present Infinitive ( amā-re ), showing the Present Stem.
3. The Perfect Indicative ( amāv-ī ), showing the Perfect Stem.
4. The neuter of the Perfect Participle ( amāt-um ), or, if that form is not in use, the Future Active Participle ( amāt-ūrus ), showing the Supine Stem.

173. The regular forms of the Four Conjugations are seen in the following.

Active— amō , amāre , amāvī , amātum [ love ]
Passive— amor , amārī , amātu
Present Stem amā-
Perfect Stem amāv-
Supine Stem amāt-

Active— dēleō , dēlēre , dēlēvī , dēlētum [ blot out ]
Passive— dēleor , dēlērī , dēlētus
Present Stem dēlē-
Perfect Stem dēlēv-
Supine Stem dēlēt-

In the Second conjugation, however, the characteristic -ē- rarely appears in the Perfect and Perfect Participle. The common type is, therefore:

Active— moneō , monēre , monuī , monitum [ warn ]
Passive— moneor , monērī , monitus
Present Stem monē-
Perfect Stem monu-
Supine Stem monit-

Active— tegō , tegĕre , tēxī , tēctum [ cover ]
Passive— tegor , tegī , tēctus
Present Stem tegĕ-
Perfect Stem tēx-
Supine Stem tēct-

Active— audiō , audīre , audīvī , audītum [ hear ]
Passive— audior , audīrī , audītus
Present Stem audī-
Perfect Stem audīv-
Supine Stem audīt-

a. In many verbs the principal parts take forms belonging to two or more different conjugations (cf. § 189).

1st and 2nd— domō , domāre , domuī , domitum [ subdue ]
2nd and 3rd— maneō , manēre , mānsī , mānsum [ remain ]
3rd and 4th— petō , petĕre , petīvī , petītum [ seek ]
4th and 3rd— vinciō , vincīre , vīnxī , vīnctum [ bind ]

Such verbs are classified according to which conjugation the Present stem belongs.