Where I can find a comprehensive explanation of the different usages of the "accusativus cum infinitivo" structure? In my Latin grammar book, I've found that it's used with verba dicendi (indirect speech), such as in

Dico te verum amicum esse

and with verba sentiendi (to express thoughts), as in the following example:

Puto te verum amicum esse.

However, having a look to other posts in this site, one can find other usages. For instance,

  • Video te venire.
  • Te beatum esse mihi est gratum.
  • Necesse est me abire.

This other example comes from this post:

Mārcus Quīntum ad terram cadere videt.

And in this answer, which explains how this construction works, we find

Sciō tē filiam ejus esse.

I've found some more examples at these slides with some explanations in Latin and Spanish. I would like to find some reading resources on the different usages of this structure, which seems to be quite common in Latin.

  • 4
    You're asking for a broad explanation for a major grammatical construction. Such an explanation might be better suited to a chapter of a Latin grammar than a QA site. I think it would be better if you asked for reading recommendations for a grammar that does justice to ACI or if you asked a specific single question about it.
    – Joonas Ilmavirta
    Commented Oct 7, 2023 at 13:46
  • OK, @JoonasIlmavirta: I've changed my question to ask for reading resources.
    – Charo
    Commented Oct 7, 2023 at 14:05

2 Answers 2


Years ago, I was taught Latin in Wheelock's Latin Grammar. It might be worth a look to get an old copy of that to work through.

There is the old, venerable, Bennett's New Latin Grammar. But, in digging through the internet trenches, it looks like Ohio State U. has the sort of resource you are looking for. It seems to do a decent job of walking through the basic and intermediate uses of the infinitive.


The de.Wikipedia article

English translation thanks to google The Latin AcI is an infinitive construction that usually depends on a verb of perception, knowledge or speaking (verba sentiendi et dicendi) or on a specific expression. It takes the position of the object and is therefore also translated with an object sentence in the form of a “that sentence”. During translation, the accusative in the name becomes the subject and the infinitive (infinitivo) becomes the main verb of the object sentence, which is introduced by the conjunction “that”. To determine the tense of the main verb, the tense of the infinitive is needed:

Infinitive (present) --> simultaneity to the main verb in the main sentence (see example 1)

Infinitive Perfect --> Prematurity of the main verb in the main sentence (cf. Example 2)

Infinitive future tense --> subsequentness to the main verb in the main sentence (see example 3)

Example 1: Num putas me scribere tantum posse? Do you think I can only write?

Example 2: Ego quoque Lucullo ingenium egregium fuisse accepi. I also learned that Lucullus’ talent was excellent.

Example 3: Spero eum mox cum militibus Romam venturum. I hope that he will come to Rome with the soldiers soon.

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