A raiz é muito longa.

A is the feminine singular definite article, meaning the.

It is used because raiz is a feminine singular noun, so a raiz means the root.

In Portuguese, articles are used more often than in English, so a sentence like this normally sounds natural with a included.

Raiz is feminine, which is why it takes a and why the adjective is longa rather than longo.

Unfortunately, you often have to learn the gender of each noun as part of the word. The ending does not always make it obvious. Even though many feminine nouns end in -a, raiz ends in -z but is still feminine.

A good habit is to learn nouns together with their article:

• a raiz
• a flor
• o livro

Because adjectives in Portuguese usually agree with the noun in gender and number.

Since raiz is feminine singular:

• masculine singular: longo
• feminine singular: longa
• masculine plural: longos
• feminine plural: longas

So:

• o caminho é longo
• a raiz é longa

É is the third person singular of the verb ser.

So it means is.

The verb ser is one of the two main Portuguese verbs that can translate English to be. In this sentence, é matches a raiz, which is singular.

Portuguese has two main verbs for to be: ser and estar.

Here, ser is used because the sentence describes a characteristic of the root: its length. That is treated as an inherent or defining quality, not a temporary state.

So:

• A raiz é muito longa. = description/characteristic

If you used estar, it would sound unusual here, because length is not normally seen as a temporary condition.

Muito means very here. It intensifies the adjective longa.

So the structure is:

• é = is
• muito longa = very long

In this use, muito is an adverb, so it does not change for gender or number:

• muito longo
• muito longa
• muito longos
• muito longas

It stays muito in all of these when it means very.

Yes. It changes when it is used as an adjective or pronoun meaning much/many, but not when it means very.

Compare:

• A raiz é muito longa.
  Here muito = very, so it does not change.

• Há muitas raízes.
  Here muitas = many, so it agrees with raízes.

This is a very common point for learners.

The accent in é serves two purposes:

1. It shows the stressed vowel sound.
2. It distinguishes é from e.

Compare:

• é = is
• e = and

So the accent is important both for pronunciation and meaning.

In European Portuguese, raiz is pronounced approximately like rah-EESH, though that is only a rough guide.

A few useful points:

• the r at the start is usually a guttural sound, not an English r
• the ai is pronounced as a diphthong
• the final z in European Portuguese is often pronounced like sh at the end of a word

So in Portugal, the ending may sound closer to -ish than to a clear English z.

This is the most normal and neutral word order:

article + noun + verb + adverb + adjective

Portuguese word order is somewhat flexible, but this version is the standard one for a simple statement.

You could change the order in special contexts for emphasis, but for learners, A raiz é muito longa is the safest and most natural pattern to use.

Usually, no. In normal Portuguese, that sounds incomplete or unnatural in this context.

You would normally say:

• A raiz é muito longa.

Leaving out the article might only happen in very specific situations, such as titles, labels, dictionary-style definitions, or highly reduced notes. In ordinary speech and writing, keep a.

You would change the noun, article, verb, and adjective so that they all agree:

• A raiz é muito longa.
• As raízes são muito longas.

Changes:

• a → as
• raiz → raízes
• é → são
• longa → longas

Notice that muito stays the same because it still means very.

Sometimes, yes. Longa and comprida can both mean long, but they are not always used in exactly the same way in every context.

For physical length, both may be possible, but longa is very common and natural here. A learner is safe using:

• A raiz é muito longa.

Later on, you can learn the small differences in usage between longo/longa and comprido/comprida depending on context and style.