La prova fotografica mostra l'errore materiale.

Because errore is a masculine singular noun that begins with a vowel. In Italian, il becomes l' before a vowel:

• il libro
• l'errore
• l'amico

So l'errore is the normal form.

Because prova is a feminine noun in Italian. That means the article and adjective must agree with it:

• la prova = the proof / evidence
• fotografica = photographic, feminine singular

So:

• la agrees with prova
• fotografica also agrees with prova

That is why you get La prova fotografica.

In Italian, adjectives often come after the noun, especially when they are more descriptive or classifying.

So:

• prova fotografica = photographic evidence / photographic proof

Putting the adjective after the noun is the most natural order here. While Italian sometimes allows adjectives before the noun, that often changes the tone or emphasis. In this sentence, prova fotografica is the standard, neutral order.

Mostra is the third-person singular present indicative of mostrare.

So it means:

• (he/she/it) shows
• demonstrates
• reveals, depending on context

In this sentence, the subject is La prova fotografica, which is singular, so the verb must also be singular:

• La prova fotografica mostra ...

Because Italian usually does not need an explicit subject pronoun when the subject is already stated or clear.

English says:

• The photographic evidence shows ...

Italian says:

• La prova fotografica mostra ...

The subject La prova fotografica is already there, so Italian does not need to add a separate word like essa. Using essa here would usually sound unnecessary or overly formal.

Not here. In this kind of context, errore materiale is a fixed expression that usually means a clerical, mechanical, or simple factual/writing error rather than a mistake of judgment or interpretation.

So materiale here does not mean:

• made of fabric/material
• physical in the everyday sense

Instead, it points to the idea of a concrete, technical, or clerical mistake.

Because in Italian, adjectives like this normally come after the noun, especially when they classify the type of thing.

So:

• errore materiale = a material/clerical error

This is the standard order. Also, errore materiale is a common set phrase, especially in formal, legal, or administrative language.

Yes. Materiale agrees with errore in number and, in this case, also matches the singular form used with masculine nouns.

Here is the pattern:

• masculine singular: errore materiale
• feminine singular: svista materiale (possible grammatically)
• masculine/feminine plural: errori materiali

A useful thing to notice is that many Italian adjectives ending in -ale have the same form in the masculine and feminine singular:

• materiale (masculine singular)
• materiale (feminine singular)
• materiali (plural)

Yes. It follows a very straightforward pattern:

• La prova fotografica = subject
• mostra = verb
• l'errore materiale = direct object

So the sentence is structurally very close to English:

• The photographic evidence shows the clerical/material error

That makes it a good example of a simple Italian declarative sentence.

Yes, in many contexts dimostra could work, but the nuance is a little different.

• mostra = shows, displays, reveals
• dimostra = proves, demonstrates more strongly

So:

• La prova fotografica mostra l'errore materiale sounds like the evidence shows/reveals the error.
• La prova fotografica dimostra l'errore materiale sounds more like the evidence proves it.

Which one is better depends on how strong you want the statement to sound.