Η πυξίδα είναι εδώ.

η is the definite article meaning the.

In this sentence, η is:

• feminine
• singular
• nominative

It matches πυξίδα, which is a feminine singular noun.

So:

• η πυξίδα = the compass

In Greek, every noun has a grammatical gender: masculine, feminine, or neuter.

πυξίδα is a feminine noun, which is why it takes the feminine article η.

This is grammatical gender, so it does not mean that a compass is biologically female. It just means the word belongs to the feminine noun class.

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

The subject is the thing that is somewhere:

• Η πυξίδα = the thing being talked about
• είναι εδώ = is here

So η πυξίδα is nominative singular.

είναι is the verb is from είμαι = to be.

Greek normally uses the verb to be in this kind of sentence, just like English does:

• Η πυξίδα είναι εδώ.
• The compass is here.

In very informal speech, headlines, or note-like language, Greek may sometimes omit it, but in normal full sentences είναι is the standard form.

είναι is the 3rd person singular form of είμαι.

That means it is used with subjects like:

• he
• she
• it
• singular nouns such as η πυξίδα

So:

• η πυξίδα είναι = the compass is

A useful detail: είναι can also be used for 3rd person plural in Modern Greek, depending on the subject.

A simple pronunciation guide is:

ee pee-KSEE-tha EE-ne e-THO

More closely:

• Η = ee
• πυξίδα = pee-KSEE-tha
• είναι = EE-ne
• εδώ = e-THO

A few sound notes:

• ξ sounds like ks
• δ sounds like th in this, not th in think
• η and ει are both pronounced ee in Modern Greek

The accent mark shows which syllable is stressed.

So:

• πυξίδα → stress on ξί
• είναι → stress on εί
• εδώ → stress on δώ

Stress matters in Greek pronunciation, and written accents are normally required in lowercase writing.

Not completely. Greek word order is more flexible than English word order.

Η πυξίδα είναι εδώ is a very natural, neutral order:

• subject + verb + adverb

But Greek can move things around for emphasis. For example, Εδώ είναι η πυξίδα could also be possible, with a different emphasis, more like:

• Here is the compass
• or The compass is here

So the sentence you have is the most straightforward neutral version.

εδώ is an adverb of place, meaning here.

It tells you where something is:

• είναι εδώ = is here

It does not change form for gender, number, or case.

Yes, very often.

Greek uses the definite article more frequently than English does. When talking about a specific thing, Greek commonly says:

• η πυξίδα rather than just
• πυξίδα

So even where English might sometimes sound natural with or without the, Greek often strongly prefers the article.

Usually it means a literal compass, but it can also be used figuratively, like in English.

For example, it can mean something like:

• a guide
• a moral compass
• a point of direction

In this sentence, though, it is most naturally understood as the ordinary physical object unless context suggests otherwise.