This is the 5364th most frequent Korean word.
두꺼운
Thick
Here, '두꺼운' describes the physical thickness of an object, the book.
두꺼운 책을 읽고 있어요.
I am reading a thick book.
In this context, '두꺼운' is used to describe the thickness of a blanket in terms of its material.
이불이 너무 두꺼워서 더워요.
The blanket is too thick, so it's hot.
Here, '두꺼운' refers to the fabric or layering thickness of clothing, implying insulation suitable for cold weather.