HOW ADVERBS ARE FORMED

Most adverbs are formed by adding -ly to an adjective:

useful  >>  usefully     slow  >>  slowly

Note these spelling changes:

-le   becomes   -ly         -->  terrible  >>  terribly
-y    becomes   -ily        -->  easy  >>  easily
-ic    becomes   -ically   -->  tragic  >>  tragically

A few common adverbs have the same form as adjectives:

early    far    fast    hard    late    next

It was a hard decision to make.  (ADJECTIVE)
You must work hard.  (ADVERB)

The adverb related to the adjective good is well:

He's a good cook.  (ADJECTIVE)
He cooks well.  (ADVERB)

ADVERBS OF MANNER  >>  How?

The coffees will turn slowly.
We choose the standard carefully.

The Adverbs of Manner tell us something extra about verbs (as if in answer to 'How?').

ADVERBS OF DEGREE  >>  How much?

Kenya coffee tends to be quite acid.
That standard we select very carefully.

The Adverbs of Degree tell us something extra about adjectives or adverbs (as if in answer to 'How much?').

Some adverbs of degree strengthen an adjective or adverb:

We select it extremely carefully.

Others make an adjective or adverb less strong:

It just makes it a little easier to register.

QUESTION:
What is the effect of these adverbs of degree: to strengthen or to make less strong?

Much finer    much more aromatic
It's fairly acid

ANSWER:
MUCH strengthens the adjectives finer and more aromatic.
FAIRLY makes the adjective acid less strong.

CONFUSING ADVERBS

MUCH

This adverb of degree can be used to strengthen comparative adjectives or adverbs, e.g. This restaurant is much more expensive. This oven cooks much less quickly.

ABSOLUTELY

This adverb of degree has a different function from adverbs like extremely and very: it is used to emphasise adjectives or adverbs whose meaning is fixed at one end of a scale, e.g. excellent or perfectly.

Such words are fixed at the end of a good-bad scale. Their meanings cannot move up and down a scale, and cannot be more or less (unlike, for example, cold or interesting). Something is either excellent, or done perfectly, or not (whereas something can be colder or less interesting).

Similar common adjectives whose meaning is fixed at one end of scale are: awful, complete, delicious, essential, impossible, right, unique, wrong. So you cannot say, e.g.  extremely delicious  or   very impossible . That is NOT correct.

Other adverbs of degree that are used like absolutely are: completely, entirely, totally, wholly, utterly.

For adjectives or adverbs that can move up and down a scale (e.g. cold, interesting, slowly) use adverbs of degree like extremely, really, or very, e.g. It's extremely cold. It's really interesting. It's cooked very slowly.

QUITE

The adverb quite can have two meanings, depending on the adjective or adverb it is used with.

1) When used with an adjective or adverb whose meaning is fixed at one end of a scale, it means completely, e.g. It's quite impossible. She sings quite perfectly.

2) Otherwise it makes an adjective or adverb less strong, e.g. The menu was quite interesting. He cooks quite well. (But see "Cultural Note" below.).

REALLY

In colloquial English really can also be used like absolutely, e.g. This cake is really delicious. The food was really awful.

CULTURAL NOTE

British English speakers are fond of understatement, that is, a statement that is restrained in ironic contrast to what might have been said. One common example of this is in their use of adverbs of degree.

British English speakers often use an adverb of degree which normally makes an adjective or adverb less strong (e.g. quite, rather) when other speakers would automatically use an adverb of degree which strengthens that word (e.g. extremely, really).

So, when an American English speaker would say, It's really cold today! a British English speaker is likely to say - of the same weather: It's rather cold today.