Adjectives and Adverbs  : 

Adjectives are used to modify nouns,
 Example : The dog is loud. – What is the dog like?  – loud

Adverbs are used to modify verbs, adjectives or other adverbs,
 Example : The dog barks loudly. – How does the dog bark? – loudly

Explanations : 

1. Comparison of Adjectives
2. Form and Comparison of Adverbs
3. Adjective or Adverb 

1-Comparison of Adjectives:

Positive Form : 

Use the positive form of the adjective if the comparison contains one of the following expressions:

as … as
Example: Jane is as tall as John.

not as … as / not so … as
Example: John is not as tall as Arnie.

Comparative Form and Superlative Form (-er/-est):

one-syllable adjectives (clean, new, cheap)
two-syllable adjectives ending in -y or -er (easy, happy, pretty, dirty, clever)

positive form	comparative form	superlative form
clean	cleaner	(the) cleanest

Comparative Form and Superlative Form (more/most):

adjectives of three or more syllables (and two-syllable adjectives not ending in -y/-er)

positive form	comparative form	superlative form
difficult	more difficult	most difficult

Comparative Form and Superlative Form (irregular comparisons) :

positive form	comparative form	superlative form
good	better	best
bad / ill	worse	worst
little (amount)	less	least
little (size)	smaller	smallest
much / many	more	most
far (place + time)	further	furthest
far (place)	farther	farthest
late (time)	later	latest
late (order)	latter	last
near (place)	nearer	nearest
near (order)	-	next
old (people and things)	older	oldest
old (people)	elder	eldest

2-Form and Comparison of Adverbs:

Adverbs are used to express how something is done (adjectives express how someone or something is).

Example: The dog sleeps quietly. The dog is absolutely quiet.

Form : 

In general: adjective + -ly :

adjective	adverb
slow	slowly

Adjectives ending in -ic: adjective + -ally (exception: public-publicly) :

adjective	adverb
fantastic	fantastically

Exceptions :

adjective	adverb (meaning)	adverb (meaning)
good	well
difficult	with difficulty
public	publicly
deep	deep (place)	deeply (feeling)
direct	direct	directly (=soon)
hard	hard	hardly (=seldom)
high	high (place)	highly (figurative)
late	late	lately (=recently)
most	most	mostly (=usually)
near	near	nearly (=almost)
pretty	pretty (=rather)	prettily
short	short	shortly (=soon)
The following adjectives are also used as adverbs (without modification):	daily, enough, early, far, fast, hourly, little, long, low, monthly, much, straight, weekly, yearly, …

3- Adjective or Adverb:

Linking Verbs:

Some verbs can only be used with adjectives, others might change their meaning when used with an adverb.

verb	used with an adjective	used with an adverb
look	look good (= appearance)	look well (= healthy)
feel	feel good (= state of health/mind)	feel well (= have a good sense of touch)
smell	smell good (= odour)	smell well (= have a good sense of smell)
taste	taste good (= preference)	taste well (= have a good sense of taste)