Comparative adjectives are used to indicate a comparison between two nouns. The comparative form is constructed by suffixing “-tar” to adjectives. There are no irregular comparative adjectives as in English “bad, worse”. The comparative suffix is used for all adjectives regardless of their length. There is nothing like English “beautiful, more beautiful” in Persian.

Formation of Comparative Adjectives

The comparative form of adjectives is constructed by suffixing تر (-tar).

Adjective Comparative Form
بزرگ
bozorg
big
بزرگتر
bozorgtar
bigger
زیبا
zibâ
beautiful
زیباتر
zibâtar
more beautiful
بدتر
bad
bad
بد
badtar
worse
آسان
âsân
easy
آسانتر
âsântar
easier
ارزان
arzân
cheap
ارزانتر
arzântar
cheaper
دوست‌داشتنی
dustdâshtani
lovable
دوست‌داشتنی‌تر
dustdâshtanitar
more lovable

Both beh and khub mean “good” but the common way of saying “good” is khub. In contrast, “better” is normally expressed with behtar.

Adjective Comparative Form
به
beh
good
بهتر
behtar
better
خوب
khub
good
خوبتر
khubtar
better

Therefore, it is incorrect to say that خوب has the irregular comparative form بهتر.

Place of Comparative Adjectives

Comparative adjectives come after the noun they modify and are related to it with the genitive marker -e. To resolve vowel hiatus, the genitive marker transforms to -ye after nouns that end in a vowel.

اتاق ارزانتر
otâgh-e arzântar
cheaper room
خانه‌ی بزرگتر
khâne-ye bozorgtar
bigger house
راه‌های ساده‌تر
râhhâ-ye sâdetar
easier ways

Comparaing A with B

To compare “A” with “B”, the following structure is used:

A Comparative از (“az”, from) B

Examples:

دشمن دانا بهتر از دوست نادان است
Doshman-e dânâ behtar az dust-e nâdân ast
A wise foe is better than a foolish friend
برادرم بزرگتر از من است
Barâdar-am bozorgtar az man ast
My brother is older than me

Persian has free word order. The comparison can be alternatively expressed using the following structure:

A از B Comparative

Examples:

دشمن دانا از دوست نادان بهتر است
Doshman-e dânâ az dust-e nâdân behtar ast
(literally: A wise foe from a foolish friend better is)
برادرم از من بزرگتر است
Barâdar-am az man bozorgtar ast
My brother is older than me
از تو قویتر است
Az to ghavitar ast
He is stronger than you