An adverb is used in two different forms: with 'ly' and without 'ly'. May I know the rules behind such usage?

1 (a) The batter drove the ball deep.

1 (b) . The play moved me deeply.

2 (a) Stay close to me.

2 (b) Examine the work closely.
1 2
I appreciate if you can educate me on this topic.
Hello Rishonly

Your question is a bit complicated and I don't think I'm a right person to answer such a question (as I'm a mere English learner at a beginner's level). But let me try if you don't mind.

1 (a) The batter drove the ball deep.
1 (b) The play moved me deeply.
You can use 'deeply' in 1 (a) also. The 'deep' makes the sentence a bit more informal than 'deeply' and emphasizes the result that the ball reached deep into the ground. In the sentence 1 (b), 'deeply' is the exclusive choice. This 'deeply' connotes 'very much' when it is used to modify a verb describing emotion. (EX) I'm deeply sorry to hear about your father's death.

2 (a) Stay close to me.
2 (b) Examine the work closely.
The sentence 2 (a) is synonymous to 'Be close to me'. So the 'close' in 2 (a) is not an adverb but an adjective. You cannot say 'Stay closely to me'. On the other hand, as for 2 (b), you can say 'Examine close the work', though the usage is rare and it sounds too much informal.

Two forms used in the same way:
cheap/cheaply, clean/cleanly, clear/clearly, close/closely, fair/fairly, fine/finely, firm/firmly, first/firstly, loud/loudly, quick/quickly, quiet/quietly, slow/slowly, thin/thinly.

Two forms used in different ways:
deep/deeply, direct/directly, easy/easily, flat/flatly, free/freely, full/fully, hard/hardly, high/highly, just/justly, last/lastly, late/lately, near/nearly, pretty/prettily, real/really, rough/roughly, sharp/sharply, short/shortly, strong/strongly, sure/surely, wide/widely.
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I'm a mere English learner at a beginner's level

You know, Paco is usually extremely accurate, but I'm not sure he understands the meaning of "beginner"! Does anyone else here think it's funny when he describes himself this way?

Paco, I hope you don't take offense at my comments -- modesty must be a Japanese virture that we Americans just don't understand. Emotion: wink
Hello Khoff

My dictionary says 'a beginner' is a person who has just begun learning something. I feel like I'm kind of professional in sewage treatment engineering but I firmly believe I'm still a beginner in learning English.
I just happened across this forum. But, I thought I'd drop a line on this:

Where two forms of an adverb exist, use the "-ly" form to answer "how?" and the root form to answer "where?" (or "to where?").

He drove the ball ... where? Deep.
The play moved him ... how? Deeply.

Students: Are you brave enough to let our tutors analyse your pronunciation?
This is from Merriam-Webster's Concise Dictionary of English Usage:

flat adverb A flat adverb is an adverb that has the same form as its
related adjective: fast in "drive fast," slow in "go slow," sure in
"you sure fooled me, " bright in "the moon is shining bright," flat
in "she turned me down flat," hard and right in "he hit the ball hard
but right at the shortstop." Flat adverbs have been a problem for
grammarians and schoolmasters for a couple of centuries now, and more
recently usage writers have continued to wrestle with them.

Flat adverbs were more abundant and used in greater variety formerly
than they are now. They were used then as ordinary adverbs and as

... commanding him incontinent to avoid out of his realm and to make
no war - Lord Berners, translation of Froissart's Chronicles, 1523

... Iwas horrid angry, and would not go - Samuel Pepys, diary, 29 May

... the weather was so violent hot - Daniel Defoe, Robinson Crusoe, 119

... the five ladies were monstrous fine - Jonathan Swift, Journal to
Stella, 6 Feb. 1712

... I will not be extreme bitter - William Wycherly, The Country
Wife, 1675

You would be hard pressed to find modern examples of these particular

Originally such adverbs had not been identical with adjectives; they
had been marked by case endings, but over the course of Middle
English the endings disappeared. The 18th-century grammarians, such
as Lowth 1762, explain how these words were adverbs. They saw them as
adjectives, and they considered it a grammatical mistake to use an
adjective for an adverb. They preferred adverbs ending in -ly.

Two centuries of chipping away by schoolmasters and grammarians has
reduced the number of flat adverbs in common use and has lowered the
status of quite a few others. Many continue in standard use, but most
of them compete with an -ly form. Bernstein 1971, for instance, list
such pairs as bad, badly; bright, brightly; close, closely; fair,
fairly; hard, hardly; loud, loudly; right, rightly; sharp, sharply;
tight, tightly. Many of these pairs have become differentiated, and
now the flat adverb fits in some expressions while the -ly adverb
goes in others. And a few flat adverbs - fast and soon, for instance
- have managed to survive as the only choice.
Adverbs of frequency need to be addressed. It is a common misconception that adverbs must always end with "ly". Words such as "always", "often", seldom", and "never", are also adverbs, but do not employ the use of "ly". These are adverbs of frequency. Others, such as "usually", "frequently", and "occasionally" are also adverbs of frequency, but these employ the traditional "ly" ending.
The above post does well to indicate what common usage does to a language. English is very much a changing language, and while these variations are accepted and understandable, they don't comply with traditional English rules. In other words, this changing language is spoken by grammaticians and ignoramouses alike, as well as by those who take liberty with their speech and writing.
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