Questa è la vostra decisione.

Questa is the feminine singular form of this.

Italian demonstratives must agree in gender and number with the noun they refer to. Here, questa refers to decisione, which is a feminine singular noun.

So:

• questo = this (masculine singular)
• questa = this (feminine singular)
• questi = these (masculine plural)
• queste = these (feminine plural)

Because decisione is feminine singular, Italian uses questa.

In Italian, possessives like mio, tuo, suo, nostro, vostro, loro are usually used with a definite article.

So Italian says:

• la vostra decisione = your decision
• literally, something like the your decision

This is normal Italian grammar.

More examples:

• il mio libro = my book
• la tua macchina = your car
• le nostre idee = our ideas

A very important exception is with many singular family members:

• mia madre = my mother
• tuo fratello = your brother

But decisione is not a family-member noun, so the article la is required.

Vostra means your, but specifically the form used with a feminine singular noun.

It agrees with decisione:

• vostro = masculine singular
• vostra = feminine singular
• vostri = masculine plural
• vostre = feminine plural

So:

• il vostro libro = your book
• la vostra decisione = your decision
• i vostri libri = your books
• le vostre decisioni = your decisions

Also, vostro/vostra can refer to:

1. more than one person being addressed: your decision = the decision belonging to all of you
2. in some formal or older-style contexts, Your as a respectful form

In modern everyday Italian, if you are speaking politely to one person, people more often use suo/sua rather than vostro/vostra.

Because è is the verb is from essere.

The accent is important because it distinguishes:

• è = is
• e = and

So:

• Questa è la vostra decisione. = This is your decision.
• pane e vino = bread and wine

In writing, you should always keep the accent on è.

Yes, decisione is feminine: la decisione.

Many Italian nouns ending in -ione are feminine, for example:

• la nazione
• la situazione
• la televisione
• la decisione

Because it is feminine, related words must match it:

• questa
• la
• vostra

That is why the whole phrase is:

• Questa è la vostra decisione.

Normally, no.

Standard Italian requires the article with possessives in cases like this, so the correct form is:

• Questa è la vostra decisione.

Leaving out la would sound ungrammatical in standard Italian.

Again, the main common exception is with singular family members:

• mia sorella
• tuo padre

But with decisione, you need la.

Yes, but the emphasis changes.

The neutral, natural version is:

• Questa è la vostra decisione.

You could also say:

• La vostra decisione è questa.

That means the same basic thing, but it puts more focus on this as the identified decision, almost like This is the decision you made or Your decision is this one.

Italian word order is a bit more flexible than English, but the most natural choice depends on what you want to emphasize.

Because questa is already doing the job of this as the subject.

In English, you might think in terms of This is your decision, where this is the subject. Italian does the same:

• Questa = this
• è = is
• la vostra decisione = your decision

So nothing is missing. Italian does not need an extra subject pronoun here.

A simple pronunciation guide is:

KWEH-sta eh la VOS-tra de-chee-ZYOH-neh

A few tips:

• qu in Italian sounds like kw
• e in questa is a clear eh
• è is also eh
• vo in vostra is stressed: VOS-tra
• ci before o in decisione sounds like ch or more exactly chee
• the stress in decisione falls on -o-: de-ci-sio-NE

If said naturally, it flows smoothly: Questa è la vostra decisione.

Yes, questa can stand on its own, as it does here.

It can function as:

1. a demonstrative adjective before a noun
   
   • questa decisione = this decision
2. a demonstrative pronoun standing alone
   
   • questa è la vostra decisione = this is your decision

So in your sentence, questa does not need another noun after it, because it already means this one or this.

The demonstrative, article, and possessive would all change to match the noun.

For example:

Masculine singular

• Questo è il vostro libro.
• This is your book.

Feminine singular

• Questa è la vostra decisione.
• This is your decision.

Masculine plural

• Questi sono i vostri libri.
• These are your books.

Feminine plural

• Queste sono le vostre decisioni.
• These are your decisions.

This is a very important pattern in Italian: words around the noun usually have to agree with it.