This book is cheaper than that book. Example Sentences London is more expensive than Madrid. This test is more difficult than the last test. Example Sentences I am happier than you. That joke was funnier than his joke.
Today is the hottest day of the summer.
This book is the cheapest I can find. Example Sentences London is the most expensive city in England. That is the most beautiful painting here. He is the most important person I know. There are some important exceptions to these rules.