Magistra dicit hoc nomen in plurali esse.

Because after a verb of saying like dicit (says), Latin very often uses an indirect statement construction:

• dicit = she says
• hoc nomen ... esse = this noun to be ...

In natural English, we translate that as:

• The teacher says that this noun is in the plural.

So Latin uses accusative + infinitive where English usually uses that + finite verb.

If Latin used est here, it would not fit the normal indirect statement construction after dicit.

It actually is accusative in sense, but the form does not change visibly here.

In an indirect statement, the subject of the infinitive is normally put in the accusative. Here that subject is hoc nomen.

The reason it does not look different is:

• hoc can be either nominative neuter singular or accusative neuter singular
• nomen can be either nominative singular or accusative singular

So hoc nomen has the same form in both cases.

A similar example with a masculine noun would show the difference more clearly:

• Magistra dicit hunc puerum adesse.
• The teacher says that this boy is present.

There you can clearly see hunc puerum in the accusative.

Because nomen is a neuter noun.

The demonstrative hic, haec, hoc must agree with the noun it modifies in:

• gender
• number
• case

Since nomen is neuter singular, the correct form is hoc.

So:

• hic = masculine
• haec = feminine
• hoc = neuter

That is why Latin says hoc nomen = this noun.

Magistra is nominative singular.

It is the subject of dicit, so it must be in the nominative:

• magistra = the teacher
• dicit = says

Together:

• Magistra dicit = The teacher says

In plurali means in the plural.

Here in takes the ablative, and plurali is ablative singular.

The phrase is shorthand for something like:

• in numero plurali = in the plural number

Often numero is simply left understood.

So in plurali esse means:

• to be in the plural
• or more naturally in English, to be plural

Because plurali is not itself a plural form here. It is an ablative singular adjective, agreeing with an implied singular noun such as numero.

So the idea is:

• in numero plurali
• literally, in the plural number

Even though the concept is plural, the grammar of the phrase is singular because numero would be singular.

This can feel strange to English speakers, but it is perfectly normal in Latin.

Nomen is a third-declension neuter noun.

Its basic forms are:

• nominative singular: nomen
• genitive singular: nominis

It means name, but in grammatical contexts it can also mean noun.

That is why in this sentence hoc nomen means this noun, not just this name.

Latin grammatical terminology often uses ordinary words in more specialized ways.

Nomen originally means name, but in grammar it can refer to a noun. In traditional Latin grammar, nomen is used broadly for a naming word.

So in a classroom or grammar context, hoc nomen is naturally understood as this noun.

Yes, the word order could be different.

Latin word order is more flexible than English because the endings show the grammatical relationships. This sentence could appear in other orders, for example:

• Magistra hoc nomen in plurali esse dicit.
• Hoc nomen magistra in plurali esse dicit.

All of these can mean essentially the same thing.

That said, the original order is very natural. Placing esse at the end is especially common in Latin.

Yes.

English usually says:

• The teacher says that this noun is in the plural.

Latin does not need a separate word for that here. Instead, it uses the indirect statement construction:

• dicit
  • hoc nomen in plurali esse

So the idea of that is built into the grammar, not expressed by a separate word.

Not in the same way.

• plurale esse would mean to be plural using an adjective directly.
• in plurali esse means to be in the plural, using a prepositional phrase.

The phrase in your sentence is idiomatic and especially natural in grammatical discussion. It focuses on the noun’s number-form.

So both ideas are related, but in plurali esse is the more exact match for to be in the plural.

Dicit is present tense, third person singular:

• he/she/it says

Because the subject is magistra, it means:

• the teacher says

So the sentence presents the teacher’s statement as happening in the present.

If it were dixit, it would mean:

• the teacher said

The demonstrative would change to match the noun’s gender, and in an indirect statement the accusative might become more visible.

For example:

• Magistra dicit hanc feminam adesse.

  • The teacher says that this woman is present.

• Magistra dicit hunc librum novum esse.

  • The teacher says that this book is new.

In your sentence, hoc nomen does not visibly change between nominative and accusative because it is neuter. With masculine or feminine nouns, the accusative is often easier to spot.