Η συναισθηματική αξία είναι μεγάλη.

A word-by-word breakdown:

• Η = the (feminine singular)
• συναισθηματική = emotional
• αξία = value
• είναι = is
• μεγάλη = big / great / significant

So the whole sentence means something like:

• The emotional value is great
• The emotional value is significant
• depending on context, even It has great sentimental value

Η is the definite article meaning the. It is the feminine singular form.

Greek articles change depending on:

• gender
• number
• case

Here, αξία is a feminine singular noun, so it takes η in the nominative singular.

Compare:

• ο άντρας = the man
• η γυναίκα = the woman
• το παιδί = the child

In this sentence, η goes with αξία, and the adjective συναισθηματική agrees with that noun.

Because they both describe the noun αξία, which is feminine.

In Greek, adjectives must agree with the noun they describe in:

• gender
• number
• case

Since αξία is feminine singular nominative, both adjectives appear in the same form:

• συναισθηματική αξία = emotional value
• μεγάλη αξία = great/significant value

If the noun were masculine or neuter, the adjective forms would change:

• μεγάλος = masculine
• μεγάλη = feminine
• μεγάλο = neuter

That is the normal position for an adjective in Greek when it directly modifies a noun: adjective + noun.

So:

• συναισθηματική αξία = emotional value

Greek can sometimes place adjectives after the noun too, but before the noun is very common and neutral here.

So this sentence sounds natural and standard.

είναι means is.

It is the 3rd person singular form of the verb είμαι = to be.

So:

• είμαι = I am
• είσαι = you are
• είναι = he/she/it is

In this sentence:

• Η συναισθηματική αξία είναι μεγάλη
  = The emotional value is great/significant

Unlike in some languages, Greek normally does use the verb to be in this kind of sentence.

In a normal full sentence like this, no, you usually keep είναι.

Greek does allow omission in some informal styles, headlines, notes, or poetic language, but the standard sentence is:

• Η συναισθηματική αξία είναι μεγάλη.

Leaving it out would sound incomplete in ordinary speech for most learners' purposes.

Literally, yes: μεγάλη is the feminine form of big / large / great.

But with abstract nouns like αξία (value), it often means:

• great
• high
• significant
• considerable

So here μεγάλη does not mean physically large. It means the value is important or substantial.

That is very common in Greek, just as English says:

• great value
• high value
• significant value

A rough pronunciation guide:

• Η = ee
• συναισθηματική = see-nehs-thee-ma-tee-KEE
• αξία = ax-EE-a
• είναι = EE-ne
• μεγάλη = meh-GHA-lee

A smoother version:

ee see-nehs-thee-ma-tee-KEE ax-EE-a EE-ne meh-GHA-lee

A few notes:

• γ before α in μεγάλη is a soft Greek g/gh sound, not exactly the English g
• the written accents show where the stress goes:
  • συναισθηματική
  • αξία
  • είναι
  • μεγάλη

Greek uses the accent mark to show which syllable is stressed.

So:

• συναισθηματική → stress on the last syllable
• αξία → stress on -ί-
• είναι → stress on the first syllable
• μεγάλη → stress on γά

Stress matters in Greek pronunciation and can sometimes distinguish words, so it is important to learn words together with their accents.

Yes, Greek word order is more flexible than English, but the neutral, standard order here is:

• Η συναισθηματική αξία είναι μεγάλη.

You may also hear variations for emphasis, such as:

• Μεγάλη είναι η συναισθηματική αξία.

This puts extra focus on μεγάλη.

But for a learner, the original order is the best and most natural pattern to use.

Often, yes, depending on context.

Literally, συναισθηματική αξία means emotional value, but in many situations English would naturally say:

• sentimental value

For example, if you are talking about an old gift, family object, or memory, sentimental value may be the best translation.

So the Greek phrase can overlap with both:

• emotional value
• sentimental value

The exact English choice depends on context.

Because in Greek the article belongs to the noun phrase as a whole, and one article is enough here:

• Η συναισθηματική αξία

That means the emotional value.

Greek can sometimes repeat the article with adjectives in other structures, but the simple and normal pattern here is:

• article + adjective + noun

So:

• η συναισθηματική αξία

is exactly what you would expect.

It is in the nominative case, because it is the subject of the sentence.

The subject is the thing that is something:

• Η συναισθηματική αξία = subject
• είναι μεγάλη = predicate

You can recognize nominative feminine singular here from forms like:

• η
• συναισθηματική
• αξία
• μεγάλη

All of them match the role and gender of the subject.

Grammatically, yes, but it means something different in emphasis.

• Η συναισθηματική αξία είναι μεγάλη
  = The emotional value is great

Here, συναισθηματική is part of the noun phrase emotional value.

But:

• Η αξία είναι συναισθηματική
  = The value is emotional

That sounds less natural in many contexts, because now you are saying that the value itself is emotional, rather than talking about a kind of value called emotional value.

So the original sentence is the better choice for the intended meaning.