Αν καθυστερείς, στείλε μου μήνυμα για να μην ανησυχώ.

If you’re late, send me a message so that I don’t worry.

Breakdown of Αν καθυστερείς, στείλε μου μήνυμα για να μην ανησυχώ.

• μου: me
• στέλνω: to send
• το μήνυμα: the message
• μην: not

Questions & Answers about Αν καθυστερείς, στείλε μου μήνυμα για να μην ανησυχώ.

Why does the sentence start with Αν?

Αν means if.

It introduces a condition: If you are late / if you’re delayed...

In everyday Greek, Αν is the normal word for if. You may also see Εάν, which is a more formal or slightly more emphatic version, but Αν is much more common in speech.

What form is καθυστερείς?

καθυστερείς is the 2nd person singular present active form of καθυστερώ, meaning to be late, to delay, or to run late depending on context.

So:

• καθυστερώ = I am late / I delay
• καθυστερείς = you are late / you are running late

Here it addresses one person informally, so it means you’re running late or you’re delayed.

Why is καθυστερείς in the present tense after Αν? Why not a future form?

In Greek, after Αν, the present tense is very often used for a real or likely future condition, especially in everyday language.

So Greek says literally something like:

If you are running late, send me a message...

Even though English may also use the present after if, learners sometimes expect a future form. Greek normally does use a future marker here.