La relazione spiega la causa e la base della decisione.

Here relazione most naturally means report, statement, or document, depending on context.

So in this sentence, La relazione is probably something like:

• a report
• an official explanation
• a written account

It does not usually mean relationship here, even though relazione can mean relationship in other contexts.

For example:

• una relazione sentimentale = a romantic relationship
• una relazione tecnica = a technical report

So you have to choose the meaning from context.

Spiega is the third-person singular form of spiegare (to explain) in the present tense.

The subject is La relazione, which is singular:

• la relazione = the report

So the verb must also be singular:

• La relazione spiega = The report explains

A quick comparison:

• La relazione spiega = The report explains
• Le relazioni spiegano = The reports explain

Italian often repeats the article before each noun in a list, especially when the nouns are separate ideas.

So:

• la causa e la base = the cause and the basis

This is very normal and natural in Italian.

You could compare:

• il padre e la madre = the father and the mother
• la forma e la struttura = the form and the structure

In English, we also often repeat the in this kind of structure. Italian does this very regularly.

Della is a contraction of:

• di
  • la = della

Here it means of the.

So:

• della decisione = of the decision

This is a very common Italian pattern:

• del = di + il
• dello = di + lo
• della = di + la
• dei = di + i
• degli = di + gli
• delle = di + le

So the last part of the sentence literally looks like:

• la base della decisione = the basis of the decision

The Italian word is decisione, and it is a feminine noun:

• la decisione = the decision

Many Italian nouns ending in -zione correspond to English words ending in -tion:

• nazione = nation
• informazione = information
• decisione = decision

So this is a useful pattern to remember. Even though the spelling is different from English, the word is closely related.

They are related, but not exactly the same.

• causa = cause, reason, what produced something
• base = basis, foundation, underlying support

So:

• la causa della decisione focuses on why the decision happened
• la base della decisione focuses on what the decision is grounded on

Using both together makes the sentence sound a bit formal and analytical. It suggests the report explains both:

1. what led to the decision, and
2. what supports or justifies it

Yes, in some contexts, but the nuance changes.

• causa often sounds a bit more objective or formal, like a cause in a chain of events
• motivo often means a reason or motive
• ragione often means reason in a broader sense

For example:

• la causa della decisione = the cause of the decision
• il motivo della decisione = the reason/motive for the decision
• la ragione della decisione = the reason for the decision

In this sentence, causa sounds fairly formal and works well in official or analytical language.

Because spiegare is a transitive verb. It can take a direct object without a preposition.

So:

• spiegare qualcosa = to explain something

Here the direct object is:

• la causa e la base della decisione

So the structure is:

• La relazione = subject
• spiega = verb
• la causa e la base della decisione = direct object

Compare:

• Il professore spiega la lezione. = The teacher explains the lesson.
• Il documento spiega il problema. = The document explains the problem.

The given word order is the most neutral and natural one:

• La relazione spiega la causa e la base della decisione.

Italian word order is often flexible, but changing it usually adds emphasis or sounds more literary or formal.

For example, you might see:

• La causa e la base della decisione le spiega la relazione.

This is grammatical, but it is much less neutral and puts emphasis on la causa e la base della decisione.

For a learner, the original order is the best model:

• subject + verb + object

It is singular because the sentence is talking about one decision:

• della decisione = of the decision

If you were talking about more than one decision, it would become:

• delle decisioni = of the decisions

So:

• La relazione spiega la causa e la base della decisione.
• La relazione spiega le cause e le basi delle decisioni.

Notice how several words change in the plural:

• la causa → le cause
• la base → le basi
• della decisione → delle decisioni

A rough pronunciation guide is:

La relazione spiega la causa e la base della decisione
lah reh-lah-TSYO-neh spyeh-gah lah KAU-zah eh lah BAH-zeh DEL-lah deh-chee-ZYO-neh

A few useful pronunciation points:

• z in relazione and decisione is part of the -zione sound, like tsyoh
• spiega begins with spi-, pronounced roughly spyeh-
• causa has the au sound, similar to cow
• decisione has stress on -o-: de-ci-sió-ne

If you want to sound natural, keep the rhythm smooth rather than pronouncing each word too separately.