Interchanging Affirmative sentence to Negative sentence and Vice versa

 In order to change an affirmative sentence into a negative one without changing its meaning, we have to use the opposite of the word used in the affirmative sentence and we have to add a negative like 'no', 'not', 'neither', 'nor', 'nothing', 'none' or 'never'. 

There is a shortcut to memorize the rules of interchanging of sentence from Affirmative to Negative and Vice versa.

 

Affirmative	Negative
1) Prefix (un, dis, im, etc)                    [impossible, unfortunate, disagree, unable]	[not possible, not fortunate, does not agree, not able ( cannot)]
2) Suffix [(less) careless, clueless, fearless, sugarless]	(does not care, has no clue, does not fear, with no sugar).
3) Use of certain words [avoid, refrain from, abstain from]	[not, Do not].
4) (love, refuse, doubtful)	Negative words + opposite word( does not hate, did not accept, not sure).
5) only, everyone	no one but (person), nothing but (this thing), but (place), [but can be replaced by except].
6) Always	never fails to be, does not fail to
7) prohibited/ forbidden from + ing. forbidden + infinitive	not allowed, not permitted
8) Sometimes	Not always ( Opposite word of Verb, Adjective, Noun)
9) Must	cannot but / cannot help
10) All	No ( Opposite word of Verb, Adjective)
11) For good/ Forever	Never   ( Opposite word of Verb)
12) Every	No ( Opposite word of Verb, Adjective)
13) Have to / has to	cannot but
14) As soon as	No sooner had
15) Many	Not a few
16) Much	Not a little
17) A Little	Not much
18) Only (person)	None but
19) Only (thing)	Nothing but
20) Only (Number/age)	Not more than/ not less than
21) For the last time	Never
22) Alone(Person)	None but
23) The best / Than any other	No other

We can change affirmative sentences to negative sentences without changing the meaning of the original sentence. 

For Example:

1) Soup is hotter than rice.
Ans. Rice is not as hot as soup.

2) Rahul was too weak to walk.
Ans. Rahul was so weak that he could not walk.

3) Sir is always on time.
Ans. Sir is never late.

4) Ganesh can run faster than me.
Ans. I cannot run as fast as Ganesh.

5) Steel is a heavy metal.
Ans. Steel is not a light metal.

6)  It is unlikely that Sachin will help you.
Ans. It is not like that Sachin will help you.

7) My bag is loose.
Ans. My bag is not tight.

8) Nitin is uncomfortable.
Ans. Nitin is not comfortable.

9) It is impossible that Suraj can run.
Ans. It is not possible that Suraj can run.

10) Nitin is totally fearless of the outcome.
Ans. Nitin does not fear the outcome.

11) Ajay is clueless about the robbery
Ans. Ajay has no clue about the robbery.

12) My brother should refrain from spending too much money.
Ans. My brother should not spend too much money.

13) Avoid making stupid things.
Ans. Do not make stupid things. 

14) Dinesh  refused the to take ice-cream.
Ans. Dinesh did not accept to take ice-cream.

15) I am doubtful of this question paper.
Ans. I am not sure of this question paper.

16) Shailesh always come here.
Ans. Shailesh never fail to come here.

17) Shyam was forbidden to come here.
Ans. Shyam was not allowed to come here.

18) Tina always tells truth.
Ans. Tina never fails to tell truth.

19) Everyone knows Sachin Tendulkar.
Ans. There is not one who does not know Sachin Tendulkar.

20) Leena was forbidden from coming here.
Ans. Leena was not allowed to come here.

21) He manages to get first prize.

Ans. He does not fail to get first prize.

22) I can't pay you.
Ans. I am unable to pay you.

23) I had not done anything.
Ans. I had yet to do something.

24) Sir, please refrain from angering her.
Ans. Sir, do not anger her. 

25) He will not be able to stop them.
Ans. He will be unable to stop them.