Este dia é especial.

Este is a demonstrative adjective. It means this and points to a specific noun: dia.

So:

• este dia = this day

In Portuguese, demonstratives usually come before the noun, just like in English:

• este livro = this book
• esta casa = this house

Because dia is masculine singular, the form is este.

Because dia is a masculine noun.

Portuguese demonstratives must agree with the noun in gender and number:

• este = masculine singular
• esta = feminine singular
• estes = masculine plural
• estas = feminine plural

So:

• este dia = this day
• esta noite = this night

Even though dia ends in -a, it is still masculine. That is one of the exceptions learners have to memorize.

Because noun gender in Portuguese is not determined only by the last letter. Many nouns ending in -a are feminine, but some are masculine, and dia is one of the common masculine exceptions.

Examples of masculine nouns ending in -a:

• o dia
• o problema
• o sistema
• o mapa

So you say:

• este dia
• um dia bonito
• o dia está lindo

You just have to learn dia as o dia.

Here é is the verb ser (to be), not estar.

Portuguese has two main verbs for to be:

• ser = for identity, characteristics, classification, more essential descriptions
• estar = for states, conditions, location, temporary situations

In Este dia é especial, especial is describing the day as being special in a defining sense, so ser is natural.

Compare:

• Este dia é especial. = This day is special.
• Ele está feliz. = He is happy.
• A porta está aberta. = The door is open.

You might sometimes hear estar especial in very specific contexts, but for this sentence é is the standard choice.

The accent in é serves an important purpose.

It helps distinguish:

• é = is
• e = and

So:

• Este dia é especial. = This day is special.
• pão e café = bread and coffee

The accent also shows the stressed vowel sound. In Brazilian Portuguese, é is usually pronounced like eh with an open vowel.

Because demonstratives like este, esse, and aquele already determine the noun.

So Portuguese normally says:

• este dia
• essa casa
• aquele carro

not usually:

• o este dia

That would sound wrong.

The demonstrative already works like this/that, so you do not need an article in front of it.

Because especial is an adjective that has the same singular form for masculine and feminine.

So:

• dia especial = special day
• noite especial = special night

In the plural, it changes to:

• dias especiais
• noites especiais

So it does agree in number, but not in gender in the singular.

Compare that with an adjective that changes more clearly:

• dia bonito
• casa bonita

But with especial, singular masculine and singular feminine are both especial.

Yes, you could, but the nuance changes.

Traditionally:

• este = this, near the speaker
• esse = that, near the listener or previously mentioned
• aquele = that over there, farther away

So:

• Este dia é especial. = This day is special.
• Esse dia é especial. = That day is special / That day you mentioned is special.

In modern Brazilian Portuguese, esse is often used a lot in everyday speech, sometimes even where older grammar would prefer este. But if the intended meaning is clearly this day, este is perfectly correct and clear.

It is grammatical and natural, but context matters.

Depending on what you mean, Brazilians might also say:

• Hoje é um dia especial. = Today is a special day.
• Este é um dia especial. = This is a special day.
• Esse dia é especial para mim. = That day is special to me.

Este dia é especial sounds fine when you are specifically pointing to this particular day.
If you mean today, then Hoje é um dia especial is often more common.

Yes, it is very close to English word order:

• Este dia = subject
• é = verb
• especial = predicate adjective

So the structure is:

This day + is + special

Portuguese often follows this same basic pattern:

• O livro é interessante. = The book is interesting.
• A casa é grande. = The house is big.

So this sentence is very straightforward for an English speaker.

A simple approximate pronunciation is:

ES-chee JEE-ah eh es-peh-see-AU

A few notes:

• este in Brazil often sounds like ES-chee or ES-tee, depending on region
• dia sounds like JEE-ah
• é sounds like eh
• especial usually has stress on the last syllable: es-peh-see-AU

A more learner-friendly breakdown:

• Este → ES-chee
• dia → JEE-ah
• é → eh
• especial → es-peh-see-AU

Pronunciation varies by region, but this will be understood well.

Yes, but only if the noun is already understood from context.

For example, if you are looking at several days on a calendar, you might say:

• Este é especial. = This one is special.

But without context, it sounds incomplete because este usually points to something specific.

So:

• Este dia é especial. = clear by itself
• Este é especial. = natural only when everyone already knows what este refers to