Comparison sentences in Greek

Question

How do we make comparison sentences in Greek?

I mean how  we can say (I am taller than you, car is more dangerous than plane)

Answer 1

Comparisons is a very large chapter in Grammar, we cannot analyze all the details in one post.  I will try to explain the very basics with some examples.

Ο Γιώργος είναι ψηλός = George is tall : We have no comparison here. The adjective tall indicates a quality that George has.

Ο Γιώργος είναι ψηλότερος από τον Κώστα = George is taller than Kostas  : Here we do have a comparison. The adjective "ψηλός" (tall) comes in a comparative degree (ending: - τερος (male) - τερη (female) - τερο (neutral)).

Then we put the preposition “από” and the noun by which the comparison is made in accusative case (τον Κώστα).

Similar examples:
Ο Νίκος είναι μεγαλύτερος από τον Γιώργο = Nikos is older than George
Η Μαρία είναι μικρότερη από την Ελένη = Maria is smaller than Helen

One of the simplest ways not to change the adjective ending is to precede it with the word  “πιο”.
Examples:
Ο Γιώργος είναι πιο ψηλός από τον Κώστα = George is taller than Kostas
Ο Νίκος είναι πιο μεγάλος από τον Γιώργο = Nikos is bigger than George
Η Μαρία είναι πιο μικρή από την Ελένη = Maria is smaller than Helen

For more information and details:
http://users.sch.gr/ipap/Ellinikos%20Politismos/Yliko/Theoria%20Nea/epitheto-parathetika.htm
http://users.sch.gr/parantoniou/site/glwssa/grammar_vathmoi_epithetwn.html