Use of Superlative Adjectives
We use a superlative adjective to describe one thing in a group of three or more things. Look at these examples:
John is 1m75. David is 1m80. Chris is 1m85. Chris is the tallest.
Canada, China and Russia are big countries. But Russia is the biggest.
Mount Everest is the highest mountain in the world.
If we talk about the three planets Earth, Mars and Jupiter