Japanese adjective doesn’t have the form of comparative and superlative like English.
When you express them in Japanese, adverb or adverbial phrase modifying adjective is used.
Comparative and “than”
(Ex) Sapporo is colder than Tokyo.
In English, adjective is changed to the form of comparative when two objects are compared.
But Japanese adjective doesn’t have the form of comparative.
So it is OK to use the original form of adjective. That’s very easy.
The Japanese word for “than” is “yori” or “yorimo”.
Because it is a particle, it is added after noun.
The phrase including “yori” or “yorimo” is an adverbial phrase.
You can put it into your favorite position in a sentence.
Sapporo is cold.
Sapporo wa samui desu.
Sapporo is colder than Tokyo.
Sapporo wa Tookyoo yorimo samui desu.
Tookyoo yori Sapporo wa samui desu.
At that time, to emphasize the subject, “no hoo” is often added to the subject.
“Hoo” means a side in some objects.
And the particle is changed to “ga”.
Sapporo no hoo ga Tookyoo yorimo samui desu.
Tookyoo yori Sapporo no hoo ga samui desu.
You can express more detailed comparison by putting the following adverb just before the adjective.
Sapporo is much colder than Tokyo.
Sapporo no hoo ga Tookyoo yorimo harukani samui desu.
This book is a little more expensive than that book. (expensive = “takai” in Japanese)
Kono hon wa ano hon yorimo sukoshi takai desu.
You can put a concrete numerical value at the position of the adverb.
This book is about 1000 yen more expensive than that book.
Kono hon wa ano hon yorimo 1000-en hodo takai desu.
Adverbs emphasizing comparative
There are a few adverbs emphasizing comparative in Japanese.
In a sense, these may be the real Japanese words to express comparative in English.
These are often used, so please learn them.
“Motto” is used in conversation frequently.
“Sarani” and “yori” sound formally a little.
Tokyo is cold today.
Sapporo is colder.
Kyoo Tookyoo wa samui desu.
Sapporo wa motto samui desu.
Of course, you can use these in the sentence with “than”.
Sapporo is colder than Tokyo.
Sapporo wa Tookyoo yori motto samui desu.
Adverbs expressing superlative
About superlative in English, you can express it by using adverb modifying adjective.
“Mottomo” is sound formally a little, and “ichiban” is a usual word.
When this expression is used, the area or range of the object is added as a adverbal phrase.
At that time, it is made by connecting with a particle.
When the area is country or region, “de” is used, and when the other case, “no naka de” is used.
Shinkansen is the fastest train in Japan. (train = ressha)
Shinkansen wa Nihon de mottomo hayai ressha desu.
He runs the fastest in his class.
Kare wa kurasu no naka de ichiban hayaku hashiri masu.
When the object is in the second or third position, you can use the adverbal phrase that the order number and “banme ni” are connected at the part of above “ichiban” or “mottomo”.
(“Banme” is written in the page of Lesson-23 as a unit word of order.)
He runs the second fastest in his class.
Kare wa kurasu no naka de ni-banme ni hayaku hashiri masu.
Kyushu is the third largest island in Japan. (large = ookii, island = shima)
Kyuushuu wa Nihon de san-banme ni ookii shima desu.