La prima impressione è importante.

La is the definite article meaning the.

In Italian, you usually use an article with nouns much more often than in English. So la prima impressione literally means the first impression.

Here:

• la = the for a feminine singular noun
• impressione is feminine singular, so it takes la

Because prima is an adjective agreeing with impressione, which is a feminine singular noun.

Italian adjectives usually change form to match the noun in:

• gender: masculine / feminine
• number: singular / plural

So:

• primo = masculine singular
• prima = feminine singular

Examples:

• il primo giorno = the first day
• la prima impressione = the first impression

In this sentence, you can tell it is feminine because it uses:

• la (feminine singular article)
• prima (feminine singular adjective)

Also, many Italian nouns ending in -ione are feminine, including:

• la nazione
• la stazione
• l’impressione

So impressione is a feminine noun: la impressione, usually shortened to l’impressione when used directly before the noun.

È is the verb essere (to be) in the third person singular: is.

The accent is important because:

• è = is
• e = and

So:

• La prima impressione è importante = The first impression is important
• without the accent, it would be a different word

This is a very common spelling point in Italian.

Some Italian adjectives have different masculine and feminine forms, while others have the same form for both genders in the singular.

Importante is one of the adjectives that has:

• importante = masculine singular or feminine singular
• importanti = plural

So:

• un libro importante = an important book
• una decisione importante = an important decision

In your sentence, importante agrees with impressione, but its singular form stays the same.

They do different jobs in the sentence.

• prima directly describes the noun impressione, so it is part of the noun phrase:
  la prima impressione = the first impression
• importante comes after è because it is the predicate adjective:
  is important

So the structure is:

La prima impressione + è + importante
subject + verb + description

This is similar to English:

• The first impression
  • is
    • important

Not in normal Italian for this meaning.

The natural phrase is la prima impressione, where prima means first in an ordering sense.

Putting prima after the noun here sounds unnatural or changes the feeling. In this expression, prima normally goes before the noun.

So the standard form is:

• La prima impressione è importante.

A simple pronunciation guide is:

La PREE-ma im-pres-SYO-ne eh im-por-TAN-te

A few notes:

• prima = PREE-ma
• impressione has stress on -o- / -syo-: im-pres-SYO-ne
• è sounds like eh
• importante has stress on -tan-: im-por-TAN-te

If you want to sound smoother, link the words together naturally: La prima impressione è importante.

Normally, no.

In standard Italian, you would usually keep the article here:

• La prima impressione è importante.

Leaving it out sounds incomplete or unnatural in this kind of sentence.

Italian generally uses articles more than English does, especially with nouns used in a general or definite way.

Grammatically, it says the first impression because of la.

But in real usage, Italian often uses the definite article where English might use a more general expression. So this sentence can express a general idea, like:

• First impressions are important
• The first impression is important

If you wanted to say a first impression more specifically, you could say:

• Una prima impressione

But your sentence is the most natural way to express the general statement.

The sentence has a very simple structure:

• La prima impressione = the subject
• è = the verb (is)
• importante = predicate adjective

So:

La prima impressione | è | importante
subject | verb | adjective

This is a very common sentence pattern in Italian:

• Il caffè è caldo. = The coffee is hot.
• La casa è grande. = The house is big.
• La prima impressione è importante. = The first impression is important.

Yes. Prima can have different uses in Italian depending on context.

In your sentence, prima is an adjective meaning first:

• la prima impressione = the first impression

But prima can also be an adverb meaning before / earlier:

• Prima mangio, poi esco. = First I eat, then I go out.
• L’ho visto prima. = I saw him earlier.

So here, because it comes before a noun and agrees with it, it is clearly an adjective.

Yes, it is completely natural and idiomatic.

La prima impressione è importante is a normal way to express the idea that first impressions matter.

Depending on context, Italians might also say:

• La prima impressione conta molto. = The first impression counts a lot.
• Le prime impressioni sono importanti. = First impressions are important.

But your sentence is clear, correct, and natural.