Positive, Comparative, Superlative

This house is big. It is also expensive. ------This house is bigger than the first. It is also more expensive.--------This house is the biggest and the most expensive of all.

Adjectives have got three forms : positive,comparative and superlative.

We use the comparative form+than to compare between two people or things. e.g. : Tom is taller than Richard. Russia is larger than Australia.

We use the superlative form+of/in to compare three or more people or things. e.g. : Chris is the tallest of all.

We use in to talk about places. e.g. : Russia is the largest country in the world.