Το ανταλλακτικό είναι στην τσάντα.

Because ανταλλακτικό is a neuter singular noun, and Greek usually uses the definite article much more regularly than English.

• το = the for a neuter singular noun
• ανταλλακτικό = spare part

So το ανταλλακτικό means the spare part.

In Greek, the article must agree with the noun in gender, number, and case.

It is neuter.

A useful clue is its ending: many neuter nouns in Greek end in -ο or -ι, but some also end in -ικό, like ανταλλακτικό.

So here:

• το ανταλλακτικό = nominative singular neuter
• του ανταλλακτικού = genitive singular neuter

Even though it refers to an object, remember that grammatical gender in Greek is a grammar category, not biological sex.

It can be both, depending on context.

As an adjective, ανταλλακτικός / ανταλλακτική / ανταλλακτικό can mean something like replacement or spare.

As a noun, το ανταλλακτικό commonly means the spare part or replacement part.

In this sentence, it is clearly being used as a noun.

είναι is the third person singular form of the verb είμαι = to be.

Since the subject is το ανταλλακτικό = the spare part, Greek uses:

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

So:

• Το ανταλλακτικό είναι... = The spare part is...

Greek does not use a separate word for it is here. The verb form είναι already tells you that.

στην is a very common contraction of:

• σε = in, at, to
• την = the, feminine singular accusative

So:

• σε την → στην

In this sentence:

• στην τσάντα = in the bag

This contraction is standard and very common in everyday Greek.

Similar forms include:

• στο = σε + το
• στον = σε + τον
• στους = σε + τους

Modern Greek normally uses the accusative after σε.

So:

• η τσάντα = the bag, nominative
• την τσάντα = the bag, accusative
• στην τσάντα = in the bag

This can feel unfamiliar to English speakers, because English does not show this kind of case marking on nouns very much.

So the structure is:

• σε + accusative
• στην τσάντα = in the bag

The dictionary form is η τσάντα = bag.

It is a feminine noun.

Its forms here are:

• η τσάντα = nominative singular
• την τσάντα = accusative singular

Because the sentence uses σε + την, you get στην τσάντα.

Greek very often uses the definite article where English also uses the, and sometimes even where English might leave it out in other contexts.

Here it is straightforward:

• στην τσάντα = in the bag

The article shows that it is a specific bag, not just any bag.

If you wanted to say in a bag, you would usually say:

• σε μια τσάντα

Yes, Greek word order is more flexible than English, because case endings and articles help show what each word is doing.

The neutral, standard order here is:

• Το ανταλλακτικό είναι στην τσάντα.

But you could also say:

• Στην τσάντα είναι το ανταλλακτικό.

That might sound more marked or emphasize where the spare part is.

English usually has to keep a stricter order, but Greek can move elements around more easily for emphasis or style.

A rough pronunciation is:

To andallaktikó íne stin tsánda.

A few helpful notes:

• το sounds like to
• ανταλλακτικό has stress on the last syllable: -κό
• είναι is usually pronounced roughly EE-ne
• στην sounds like stin
• τσ in τσάντα sounds like ts in cats
• τσάντα has stress on the first syllable: TSAN-da

Greek stress matters, so notice:

• ανταλλακτικό
• τσάντα

Greek uses accent marks to show the stressed syllable of a word.

• είναι is stressed on the first syllable
• το is a very short unstressed article, so it has no accent

Likewise:

• ανταλλακτικό
• τσάντα

Learning where the stress goes is important, because stress is part of the correct spelling and pronunciation in Greek.

No, not in a normal sentence like this. In Modern Greek, the verb to be is usually expressed.

So you say:

• Το ανταλλακτικό είναι στην τσάντα.

Not:

• Το ανταλλακτικό στην τσάντα.

Greek does sometimes omit things in very informal notes, headlines, or special contexts, but in ordinary full sentences you should keep είναι.

You would usually say:

• Το ανταλλακτικό είναι σε μια τσάντα.

Here:

• σε = in
• μια = a, one
• τσάντα = bag

So:

• στην τσάντα = in the bag
• σε μια τσάντα = in a bag

That is a useful contrast to remember.

Not always. σε is a very flexible preposition and can mean:

• in
• at
• to
• sometimes other related location/direction meanings depending on context

For example:

• στο σπίτι = at home / in the house
• στο σχολείο = at school / to the school, depending on context
• στην τσάντα = in the bag

So you should learn σε as a general preposition of location or direction, not as a word with only one fixed English translation.