Hoy es especialmente importante.

Spanish often leaves out subject pronouns when they are not needed. In English, you usually need a subject, so you say It is especially important today. In Spanish, that it is often not expressed.

Here, es importante works as an impersonal statement: is important. The sentence is understood from context, so Spanish does not need a separate subject word.

Because ser is normally used for judgments, definitions, and general statements like it is important, while estar is more often used for states, conditions, or locations.

So:

• Es importante = It is important
• Está importante = not natural here

With this kind of statement, Spanish uses ser:

• Es necesario
• Es difícil
• Es importante

Hoy means today, and here it sets the time for the whole statement.

So the sentence structure is basically:

• Hoy = today
• es = is
• especialmente importante = especially important

Starting with hoy is very natural, because Spanish often puts time expressions at the beginning of the sentence.

Yes. Spanish allows some flexibility.

For example:

• Hoy es especialmente importante.
• Es especialmente importante hoy.

Both are grammatical, but the focus changes a little:

• Hoy es especialmente importante emphasizes today
• Es especialmente importante hoy sounds more like the speaker is adding today at the end for contrast or emphasis

The version with hoy at the beginning is the most neutral and natural here.

Especialmente is an adverb. It means especially.

It comes from the adjective especial plus the ending -mente, which is a very common way to form adverbs in Spanish:

• rápido → rápidamente
• normal → normalmente
• especial → especialmente

So especialmente importante means especially important.

Because especialmente is an adverb, and adverbs do not change form.

Also, importante is an adjective that has the same form for masculine and feminine singular:

• un día importante
• una decisión importante

Only the plural changes:

• días importantes
• decisiones importantes

So in this sentence, importante stays exactly as it is.

Yes, but it means something a bit different.

• muy importante = very important
• especialmente importante = especially important

Muy just increases the degree. Especialmente suggests special significance, often compared with other times or situations.

So:

• Hoy es muy importante = today is very important
• Hoy es especialmente importante = today is especially important

Yes, it is a complete sentence.

Spanish often uses short impersonal sentences like this:

• Es verdad
• Es posible
• Es importante

Adding hoy and especialmente just gives more information. Even without a visible subject, the sentence is fully natural and complete.

Because especialmente modifies the adjective importante, and in Spanish adverbs usually come before the adjective they modify.

So:

• especialmente importante = especially important

This is the normal order.

A version like importante especialmente would sound unnatural here unless it appeared in a very specific structure.

In standard Spain Spanish, it would sound roughly like:

oy es espe-thyal-MEN-tee im-por-TAN-teh

A more precise pronunciation is:

/oi es espeθjalˈmente impoɾˈtante/

A few useful notes:

• h in hoy is silent
• y in hoy sounds like the y in boy
• in much of Spain, c before i is pronounced like th in thin, so especialmente has that th sound
• the stress falls on -men- in especialmente and on -tan- in importante

Yes. Depending on context, English might say either:

• It is especially important today
• Today is especially important

Spanish does not force the same choice that English does. Hoy es especialmente importante can match either one, depending on what the speaker means in context.

No. Here hoy is an adverb of time, not a noun.

It tells you when something is true: today.

That is why there is no article:

• hoy = today

If you use a noun expression, the structure is different, for example:

• el día de hoy = this day / today

But in normal everyday Spanish, hoy by itself is the most natural choice here.