Η φίλη μου ξέχασε το τάπερ της στο ψυγείο του γραφείου.

In Greek, it is very normal to say article + noun + possessive, so:

• η φίλη μου = my friend
• literally, something like the friend of mine

Unlike English, Greek usually keeps the definite article in this kind of phrase. So η φίλη μου is the standard way to say my friend.

μου is the weak genitive form of εγώ (I / me), and in this sentence it means my.

So:

• η φίλη μου = my friend

Greek often uses these short genitive pronouns after the noun:

• μου = my
• σου = your
• του / της = his / her / its
• μας = our
• σας = your
• τους = their

They come after the noun much more often than English speakers expect.

Because they refer to two different possessors:

• η φίλη μου = my friend
• το τάπερ της = her container

So the sentence talks about:

1. my friend
2. her container

In context, της most likely refers back to my friend, so the idea is that my friend forgot her container.

That is the normal Greek pattern. Greek usually expresses possession like this:

• το βιβλίο μου = my book
• η τσάντα της = her bag
• το τάπερ της = her container

So the possessive pronoun usually follows the noun.

English speakers often want to put the possessive first, but in Greek the post-noun position is the basic one.

ξέχασε is the 3rd person singular aorist of ξεχνάω / ξεχνώ.

Here it means forgot.

Why the aorist? Because the sentence describes a single completed event: she forgot it. Greek commonly uses the aorist for that kind of whole action.

So:

• ξεχνάει = she forgets / is forgetting
• ξεχνούσε = she was forgetting / used to forget
• ξέχασε = she forgot

Because the sentence is about one complete action, not an ongoing or repeated one.

• ξέχασε presents the act as a finished event.
• ξεχνούσε would sound like an ongoing past situation or a habitual one.

In English, forgot is also the natural choice here, and Greek matches that with the aorist.

Yes, τάπερ is very common in everyday Greek. It comes from Tupperware, but in modern spoken Greek it usually means a plastic food container / lunch container in general.

A few useful points:

• It is very common in conversation.
• It is treated as neuter: το τάπερ
• It is often used even when the container is not actually the Tupperware brand.

So this is a very natural modern Greek word.

Loanwords in Greek are often assigned a grammatical gender, and τάπερ is commonly treated as neuter.

That is why you get:

• το τάπερ
• το τάπερ της

You do not need to look for a deep logical reason every time; with borrowed nouns, the gender is often just something you learn together with the word.

στο is a contraction of:

• σε + το = στο

Here σε means something like in / at / to, depending on context.

So:

• στο ψυγείο = in the fridge

This contraction is extremely common:

• στο = σε + το
• στη = σε + τη(ν)
• στον = σε + τον

In Modern Greek, prepositions like σε normally take the accusative.

So after σε, you expect the accusative form. Here that is:

• το ψυγείο → στο ψυγείο

Because ψυγείο is a neuter noun, its nominative and accusative look the same, so you do not see a visible change. But grammatically, it is accusative after σε.

του γραφείου is a genitive phrase, and it shows a relationship like of the office.

So:

• το ψυγείο του γραφείου = the office’s fridge
• more literally, the fridge of the office

This is a very common Greek structure:

• η πόρτα του σπιτιού = the door of the house
• το κλειδί του αυτοκινήτου = the key of the car
• το ψυγείο του γραφείου = the fridge of the office

It can mean either, depending on context.

• γραφείο = office
• γραφείο = desk

In this sentence, because we have το ψυγείο του γραφείου, the natural meaning is the office fridge, so γραφείου is understood as office, not desk.

Context usually makes the meaning clear.

Yes. Greek word order is more flexible than English word order.

The given sentence is a very natural neutral order:

• Η φίλη μου ξέχασε το τάπερ της στο ψυγείο του γραφείου.

But Greek can move things around for emphasis, topic, or style. For example, you might hear variants that emphasize the container or where it was forgotten.

Even so, the version you have is a good standard pattern for learners.

In normal context, that is the most likely reading: my friend forgot her container.

But grammatically, της just means her. So in a different context, it could refer to another female person already mentioned.

So:

• το τάπερ της = her container
• who her is depends on context

In this sentence by itself, most people will naturally connect της with η φίλη μου.

You would change η φίλη μου to ο φίλος μου:

• Ο φίλος μου ξέχασε το τάπερ του στο ψυγείο του γραφείου.

Changes:

• η φίλη → ο φίλος
• της → του if the container is his

So this sentence is also a good example of how Greek marks gender in nouns, articles, and possessive pronouns.