Τον χειμώνα η φίλη μου παίρνει βιταμίνη C, γιατί παθαίνει εύκολα συνάχι.

Τον χειμώνα is a very common Greek time expression meaning in winter or during the winter.

Greek often uses the accusative for expressions of time:

• ο χειμώνας = winter
• τον χειμώνα = in winter / during winter

So this is not a direct word-for-word the winter in the English sense. It is just the normal Greek way to express time here.

It depends on context, but in this sentence it most naturally means in winter / during the winter season, as a habitual situation.

Because the verbs are in the present tense and describe something she regularly does, the whole sentence sounds like:

• In winter, my friend takes vitamin C, because she easily gets a cold.

So here it is more general/habitual than a single specific winter.

In Greek, the unstressed possessive forms like μου, σου, του, της, μας, σας, τους usually come after the noun:

• η φίλη μου = my friend
• το σπίτι μου = my house
• ο αδερφός της = her brother

This is the normal pattern. Greek also usually keeps the article:

• η φίλη μου, not just φίλη μου in most neutral contexts.

Παίρνει is the 3rd person singular present of παίρνω.

So:

• παίρνω = I take
• παίρνεις = you take
• παίρνει = he/she/it takes

Here it matches η φίλη μου, so it means my friend takes.

Yes. Greek normally uses παίρνω for taking medicine, vitamins, pills, etc.

Examples:

• παίρνω φάρμακα = I take medicine
• παίρνω αντιβίωση = I take antibiotics
• παίρνω βιταμίνη C = I take vitamin C

So this is very natural Greek.

Greek often omits the article with things like medicines, substances, and general objects when speaking in a broad or routine way.

So:

• παίρνει βιταμίνη C = she takes vitamin C

This sounds natural when you mean it generally, not as a specific identified bottle/dose. If you said τη βιταμίνη C, it could sound more specific, like a particular vitamin C already known from context.

Because Greek, like English, often uses the present tense for habitual actions.

So:

• η φίλη μου παίρνει... = my friend takes...
• παθαίνει... = she gets...

This does not mean only right now. It means this is something that usually happens.

Παθαίνω is a very common Greek verb meaning something like:

• to suffer
• to get
• to have happen to you

With illnesses or unpleasant conditions, it often means to get or to come down with something.

So here:

• παθαίνει συνάχι = she gets a cold / she comes down with a cold

It is a very natural choice in everyday Greek.

Because εύκολα is an adverb, and it modifies the verb παθαίνει.

• εύκολος / εύκολη / εύκολο = easy (adjective)
• εύκολα = easily (adverb)

So:

• παθαίνει εύκολα συνάχι = she easily gets a cold

In more natural English, that often means:

• she gets colds easily
• she is prone to getting a cold

Συνάχι usually refers to a cold, especially with the sense of sniffles / runny nose / stuffy nose.

It is close to κρυολόγημα, but they are not always felt as exactly identical:

• κρυολόγημα = a cold, more generally
• συνάχι = often emphasizes the nasal symptoms

In many everyday contexts, though, learners can understand συνάχι simply as a cold.

Greek often leaves out the article with illnesses or conditions in expressions like this, especially after verbs such as παθαίνω.

So:

• παθαίνει συνάχι = she gets a cold

This is natural and idiomatic. You could sometimes hear ένα συνάχι, but that would sound more like a case of a cold or would add a slightly different emphasis.

Here γιατί means because.

Greek γιατί can mean either:

• why?
• because

In this sentence, it clearly means because:

• ..., γιατί παθαίνει εύκολα συνάχι.
• ..., because she easily gets a cold.

Yes, επειδή could also be used in many contexts:

• ..., επειδή παθαίνει εύκολα συνάχι.

Both can mean because, though γιατί is extremely common in everyday speech.

Greek word order is fairly flexible. This sentence begins with Τον χειμώνα to set the time frame first.

The given order is:

• Τον χειμώνα η φίλη μου παίρνει βιταμίνη C...

But other orders are also possible, for example:

• Η φίλη μου παίρνει βιταμίνη C τον χειμώνα...

The original version sounds natural because Greek often places time expressions at the beginning when they are the topic or setting of the sentence.