adverb comparison

vikram4689 wrote:

Do not compare an adverb that ends in -ly by changing the ending to -er: This error is common in speech. Instead, add more.
Wrong: Adrian runs QUICKLY. He runs QUICKER than Jacob.
Right: Adrian runs QUICKLY. He runs MORE QUICKLY than Jacob.

However, some adverbs that do not end in -ly are made into comparatives by adding -er:
Right: Adrian runs FAST. He runs FASTER than Jacob.

Above quote is from mgmat sc. I did not get what is the gist of this quote.
1) why QUICKER is wrong, both QUICKER and QUICKLY are ADVERB
2) according to rule stated, how FASTER is correct as FASTLY exists ( https://www.merriam-webster.com/dictionary/fastly )

Quick is an ADJ and Quickly is an ADV. They are different parts of speech and thus cannot be used interchangeably. We must say I write more quickly than John. and John writes more slowly than I do. WE MUST USE AND ADV TO MODIFY THE VERB WRITE. Now, we can say I am more quick than John. This is because we use the verb be and thus quick modifies the noun I (rather than the verb)

Fast is both an ADJ and an ADV. As a result we can use the +er comparison form correctly for both ADV and ADJ.

I run faster than John (ADV)
I am faster than John (ADJ)

Does this help

alex.gellatly wrote:

vikram4689 wrote:

Do not compare an adverb that ends in -ly by changing the ending to -er: This error is common in speech. Instead, add more.
Wrong: Adrian runs QUICKLY. He runs QUICKER than Jacob.
Right: Adrian runs QUICKLY. He runs MORE QUICKLY than Jacob.

However, some adverbs that do not end in -ly are made into comparatives by adding -er:
Right: Adrian runs FAST. He runs FASTER than Jacob.

Above quote is from mgmat sc. I did not get what is the gist of this quote.
1) why QUICKER is wrong, both QUICKER and QUICKLY are ADVERB
2) according to rule stated, how FASTER is correct as FASTLY exists ( https://www.merriam-webster.com/dictionary/fastly )

Quick is an ADJ and Quickly is an ADV. They are different parts of speech and thus cannot be used interchangeably. We must say I write more quickly than John. and John writes more slowly than I do. WE MUST USE AND ADV TO MODIFY THE VERB WRITE. Now, we can say I am more quick than John. This is because we use the verb be and thus quick modifies the noun I (rather than the verb)

Fast is both an ADJ and an ADV. As a result we can use the +er comparison form correctly for both ADV and ADJ.

I run faster than John (ADV)
I am faster than John (ADJ)

Does this help

I looked up various websites to find out the difference. Some said that although QUICKER is an adjective/adverb but as per common usage after 1970, MORE QUICKLY is used for verb comparison and yes the reason was same that you mentioned.

As far as FASTLY is concerned, i don't think it is a WORD in existence but somehow dictionary shows it. What do you think ...