As ... as, Than & The

These small words hold comparisons together:

• as ... as says two things are equal: He is as tall as his father. With not, it means "less": The exam wasn't as difficult as I expected.
• than comes after a comparative: older than me, better than the book. Never use as or then after a comparative.
• the comes before a superlative: the best café, the largest country.
• more goes before long adjectives, adverbs and nouns: more crowded, more slowly, more money. Less is its opposite and also works with short adjectives: less tired, less sugar.
• the most marks the top of a group: the most expensive hotel.

Read the whole sentence to choose between more and less: the second sentence often tells you which one fits.