Ο κίνδυνος είναι μεγαλύτερος όταν έχει παγετό.

Greek uses the definite article much more often than English does. So Ο κίνδυνος is perfectly natural even in a general statement.

Here it marks κίνδυνος as the subject of the sentence: the danger / the risk. In English, you might sometimes translate this more naturally as just danger or the risk, depending on context.

κίνδυνος is masculine singular nominative.

You can tell because:

• ο is the masculine singular nominative form of the
• -ος is a very common ending for masculine singular nominative nouns

Since it is the subject of the sentence, the nominative case is exactly what we expect here.

μεγαλύτερος is the comparative form of μεγάλος (big, great). Here it means greater.

It has the ending -ος because it must agree with κίνδυνος, which is:

• masculine
• singular
• nominative

So:

• ο κίνδυνος → masculine singular nominative
• μεγαλύτερος → masculine singular nominative

Greek adjectives, including comparative ones, agree with the noun they describe.

Yes. πιο μεγάλος is also correct and very common.

So these are both possible:

• Ο κίνδυνος είναι μεγαλύτερος
• Ο κίνδυνος είναι πιο μεγάλος

Both mean the danger is greater / bigger.

Very roughly:

• μεγαλύτερος is a one-word comparative
• πιο μεγάλος is an analytic comparative, like more big in structure, though of course it is normal Greek

In this sentence, μεγαλύτερος sounds completely natural.

όταν means when or whenever.

In this sentence, it introduces a time clause:

• όταν έχει παγετό = when / whenever there is frost

Because the whole sentence is a general statement, English often translates όταν here as when or whenever.

This is a very common Greek pattern. Greek often uses έχει in impersonal expressions about weather or conditions.

For example:

• έχει κρύο = it is cold
• έχει ζέστη = it is hot
• έχει ομίχλη = it is foggy / there is fog
• έχει παγετό = there is frost / it is frosty

So although the literal wording is has frost, the real meaning is an impersonal weather expression.

Because παγετό is the accusative form, used after έχει.

The noun is:

• nominative: ο παγετός
• accusative: τον παγετό

In έχει παγετό, the noun works as the object of έχει, so the accusative is used.

This is a very useful pattern to notice: the article is omitted here, but the noun still appears in the accusative form.

There is no expressed subject, and that is normal.

In English, we often need a dummy subject:

• it is cold
• there is frost

Greek often does not use a dummy subject in the same way. So έχει παγετό works by itself as an impersonal expression.

Also, Greek regularly leaves out subject pronouns when they are unnecessary, because the verb form already carries person and number information.

The present tense here expresses a general truth or usual situation.

So the sentence means something like:

• The danger is greater when there is frost
• The danger is greater whenever there is frost

It is not necessarily talking about only one specific moment. It describes what is generally true.

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

You could also say:

• Όταν έχει παγετό, ο κίνδυνος είναι μεγαλύτερος.

This means the same thing. The difference is mostly one of emphasis and flow.

• Ο κίνδυνος είναι μεγαλύτερος όταν έχει παγετό starts with the main statement
• Όταν έχει παγετό, ο κίνδυνος είναι μεγαλύτερος starts with the condition

Both are natural.

A rough English-friendly pronunciation would be:

o KIN-thi-nos EE-ne me-ga-LI-te-ros O-tan E-hi pa-ge-TO

A few useful notes:

• κίνδυνος has the stress on κίν-
• είναι is stressed on εί-
• μεγαλύτερος is stressed on -λύ-
• όταν is stressed on ό-
• έχει is stressed on έ-
• παγετό is stressed on the last syllable: -τό

The written accents in Greek show you exactly where the stress goes.