Comparatives and superlatives

Adjectives

We use comparative and superlative adjectives to compare objects of the same type. For instance,

These seats are better than seats in the back, but seats right next to the stage are the best.
These seats are also more expensive than seats in the back, but seats next to the stage are the most expensive.
That pine is taller than the oak next to it. The oak is shorter (than the pine).
Giant sequoias are the tallest trees.

Notice that:

the comparative forms—better, more expensive, taller, shorter—are used without a preceding article, but with the explicit or implied succeeding preposition, than;
the superlative forms—best, most expensive, tallest—are used with a preceding definite article, the, but are not followed by a succeeding preposition;
two systems are used to form comparatives and superlatives: those that use suffixes er and est, and those that use quantifiers—such as more, less, most.

Some comparatives and superlatives are completely irregular, in that we cannot predict their forms from their basic (positive) forms:

We use *much*, *little*/*less*/*least* for continuous items, and *many*, *few*/*fewer*/*fewest* for countable items. We use *farther* and *farthest* for literal distances, and *further* and *furthest* in metaphor.
Positive form	Comparative form	Superlative form
good	better	best
bad	worse	worst
much many	more	most
little few	less fewer	least fewest
far	farther further	farthest furthest

Although some irregularities remain for other comparatives and superlatives, they tend to follow two systems:

For adjectives with one syllable and many with two syllables (usually those ending in the letter y), the rules for obtaining the comparative and superlative can be extracted from the folowing examples:

free − e + er → freer (comparative; freeer would have too many es, so we drop one);
free − e + est → freest (superlative; again, freeest would have too many es, so we drop one);

happy − y + ier → happier (comparative; if the y were not replaced with i, the word would be pronounced as happ'yer—which confuses the root word—as opposed to happ'i'er, which does not);
happy − y + iest → happiest (superlative; again, if the y were not replaced with i, the word would be pronounced as happ'yest rather than happ'i'est);

tall + er → taller (comparative);
tall + est → tallest (superlative).

The final effect is that, for these adjectives, the comparatives always end with er, and the superlatives always with est.

For many adjectives with two syllables and adjectives with three or more syllables, a completely different system is used:

expensive (ex'pen'sive)
→ more expensive, less expensive (comparative forms);
→ most expensive, least expensive (superlative forms).

That is, we prefix the adjective with more or less for the comparative, and with most or least for the superlative. For two-syllable words, the choice between which of the two methods to use is idiomatic:

simple (two syllables: sim'ple)
→ simpler;
→ simplest;

joyful (two syllables: joy'ful)
→ more joyful;
→ most joyful.

We never combine the two systems described, unless we intend humorous exaggeration. Thus we almost never say most driest, but rather just driest. If we want to clarify that something is drier than something else that is claimed to be the driest, we use the adverb even; for instance,

I think the Gobi is the driest desert on Earth.
No, the Atacama is even drier.

Adverbs

We use comparative and superlative adverbs to compare actions, states or occurrences expressed as verbs. For instance,

He has studied better than last time, so he will do better (than last time) on his exams.
The least rapidly growing plant we have is a serviceberry.

The exceptions as well as the rules for forming comparative and superlative adverbs are similar to those for adjectives, but simpler.

Corresponding to the completely irregular adjectives, we have the completely irregular adverbs:

We use *farther* and *farthest* for literal distances, and *further* and *furthest* in metaphor.
Positive form	Comparative form	Superlative form
well	better	best
badly	worse	worst
much	more	most
little	less	least
far	farther further	farthest furthest

However, the comparative and superlative forms of most adverbs follow one of two systems:

Adverbs that obtain their forms from adjectives by appending the suffix ly are: always modified with more or less to obtain their comparative forms; and with most or least to obtain their superlative forms. Thus, for example,

quickly
→ more quickly / less quickly;
→ most quickly / least quickly;

joyfully
→ more joyfully / less joyfully;
→ most joyfully / least joyfully.

It is important to note that there are adverbs that end in ly that aren't obtained from an adjective by adding this suffix. An example is early. For these adverbs, and for adverbs that don't end in ly, we obtain the respective comparatives and superlatives using the first system explained in the previous section. Thus,

early
→ earlier;
→ earliest;

late
→ later;
→ latest;

fast
→ faster;
→ fastest.