Έλεγξαν όχι μόνο διάτρηση αλλά και χαρακτηριστικό ασφαλείας.

They checked not only perforation but also a security feature.

Breakdown of Έλεγξαν όχι μόνο διάτρηση αλλά και χαρακτηριστικό ασφαλείας.

• όχι μόνο ... αλλά και: not only ... but also
• ελέγχω: to check
• η διάτρηση: the perforation
• το χαρακτηριστικό ασφαλείας: the security feature

Questions & Answers about Έλεγξαν όχι μόνο διάτρηση αλλά και χαρακτηριστικό ασφαλείας.

What does Έλεγξαν mean grammatically?

Έλεγξαν is the aorist active, 3rd person plural form of ελέγχω (to check, to inspect, to verify).

So it means they checked.

A few useful points:

• 3rd person plural = they
• aorist = a completed action, viewed as a whole
• In this sentence, it presents the checking as a finished event: they checked ...

Why is there no word for they in the sentence?

Greek often drops subject pronouns when the verb ending already shows who the subject is.

So:

• Έλεγξαν already means they checked
• adding αυτοί (they) would usually only be done for emphasis or contrast

This is very normal in Greek. English usually needs they, but Greek often does not.

How does όχι μόνο ... αλλά και ... work?

This is the Greek equivalent of not only ... but also ...

In your sentence:

• όχι μόνο διάτρηση
• αλλά και χαρακτηριστικό ασφαλείας

So the structure is:

• όχι μόνο X αλλά και Y
• not only X but also Y

It is a very common pattern in Greek, just as in English.

Why are διάτρηση and in the same form? What case are they?