IF vs WHEN

if or when When we are using if or when in the sense of whenever, in other words to talk about repeated predictable actions, it doesn't matter which we use as there is very little difference in meaning. Compare the following: When I'm broke, I borrow money from my mother. I borrow money from my mother if I'm hard-up. Whenever I'm short of cash, I borrow money from my mother. I always feel sick if I go for a ride in your car. I always feel nauseous when I go for a ride in your car. I always feel queasy whenever I go for a ride in your car. when not if If it is certain that something has happened, is happening or will happen, we have to use when: When I arrived back home, Sandra was no longer there. You can have a drink when we get to Julie's place. Not now, when you're driving. if not when If it is uncertain that something has happened or will happen, we have to use if: He'll be here soon, if he caught the 1.30 train. If I manage to get to Argentina next year, I'll come and visit you. It is in this sense that the meaning corresponds to in the eventthat or in case of. We sometimes use these expressions instead of if, if we wish to sound more formal. Compare the following: In the event that you are unable to fly on 1 May, I would advise you to buy a travel ticket with greater flexibility. What happens if you can't fly on 1 May? Don't buy a travel ticket which limits your options. In case of frost, the race meeting will be cancelled. If frost is forecast, the race meeting will be called off.

			if or whether Restrictions also operate in the use of if and whether. If andwhether, of course, always imply uncertainty. You can generally use if or whether when you are reporting yes/no questions. It doesn't matter which you choose: Can you take care of Tommy for me? ~ I don't know yet whether / if I shall be able to look after Tommy during the Easter holidays or not. Is Paco still around? I wondered whether / if Paco had left the country as I hadn't seen him for some time. whether not if However, after prepositions, before to-infintives, inwhether…or… constructions and whenever we start a sentencewith the conjuntion, we have to use whether: Whether I'll get there in time for Henry's lecture, I don't know. I can't make up my mind whether to buy some new summer clothes now or wait until the prices go down.. There was a lot of discussion about whether Ringo should have his tongue pierced or not. Whether we go by bus or by train doesn't really matter. It's bound to be a slow journey. I'm going to spend all of granny's money on a new kitchenwhether you like it or not!

			if not when in 'conditional' sentences In 'conditional' sentences, we normally use if. If we are describing something which must happen first so that something else can occur, i.e. referring to a condition for something to happen, we have to use if, unless if means whenever. Consider these three conditional sentences below and then scroll back to the very first examples to remind yourself about if meaning whenever: I'll help you landscape the garden, if I can get off work for a couple of weeks. Don't take any chances. What would you do if you lost your job? If my dad had been alive, he would've sorted it all out for you in a matter of days.

From Different sources

When or if? 
We use when for things that are certain to happen in the future: 

I’ll buy you a pair of gloves when I go shopping this afternoon. 
I’ll give you a ring when I get home from school. 
Note that although the reference is clearly to the future, we use the present tense in the when-clause. 

We use if for things that may happen and which we are not certain about: 

If I decide to come to London this year, I’ll come and visit you. 

I’m going to call the police if she’s not back within the hour. 

If you make the salads, I’ll prepare the barbecue. 
In all of these examples, we are talking about future conditions and whether we use when or if depends upon the certainty of things happening. 

However, when and if are interchangeable when we are talking about general conditions that always apply when if means almost the same as whenever. Compare the following: 

I keep the air-conditioning on at night if the temperature goes above 30 degrees. 

I keep the air-conditioning on at night whenever / when the temperature goes above 30 degrees. 

If the green flag is flying, it’s quite safe to swim here 
You can swim here whenever / when / provided the green flag is flying. 

if vs. when

if and when are interchangeable when the statement of the conditional clause is a fact or a general issue (also known as zero conditonal)
If you heat ice, it melts.
When you heat ice, it melts.

if is used for something that, according to the speaker, might happen.
We can spend the afternoon on the beach if the weather is fine.

when is used for something that, according to the speaker, will happen.
I will clean up the kitchen right away when I'm back from work.

in case vs. if

in case of can be used to shorten an if-clause as shown below:
If there is a fire, leave the room.     In case of fire, leave the room.

While if expresses a condition (1), in case is used to express a possibility (2).
(1)     I need painkillers if I'm in severe pain.
(2)     I need painkillers in case I'm in severe pain.

The expression just in case is used pretty much the same way.
I got you a pizza just in case you were hungry.
(I don't know whether you are hungry.)


Example: 
Represented by widening income and standard of living gaps, increasing economic disparity, when exacerbated simultaneously by population growth, often leads to social unrest and rioting.

A. when exacerbated simultaneously by population growth, often leads
B. when exacerbated by simultaneously grown population, often lead
C. when being exacerbated by simultaneous growth in population, often leads
D. if exacerbated simultaneously by population growth, often lead
E. if exacerbated by simultaneous population growth, often leads 

IF vs WHEN

if or when When we are using if or when in the sense of whenever, in other words to talk about repeated predictable actions, it doesn't matter which we use as there is very little difference in meaning. Compare the following: When I'm broke, I borrow money from my mother. I borrow money from my mother if I'm hard-up. Whenever I'm short of cash, I borrow money from my mother. I always feel sick if I go for a ride in your car. I always feel nauseous when I go for a ride in your car. I always feel queasy whenever I go for a ride in your car. when not if If it is certain that something has happened, is happening or will happen, we have to use when: When I arrived back home, Sandra was no longer there. You can have a drink when we get to Julie's place. Not now, when you're driving. if not when If it is uncertain that something has happened or will happen, we have to use if: He'll be here soon, if he caught the 1.30 train. If I manage to get to Argentina next year, I'll come and visit you. It is in this sense that the meaning corresponds to in the eventthat or in case of. We sometimes use these expressions instead of if, if we wish to sound more formal. Compare the following: In the event that you are unable to fly on 1 May, I would advise you to buy a travel ticket with greater flexibility. What happens if you can't fly on 1 May? Don't buy a travel ticket which limits your options. In case of frost, the race meeting will be cancelled. If frost is forecast, the race meeting will be called off.

			if or whether Restrictions also operate in the use of if and whether. If andwhether, of course, always imply uncertainty. You can generally use if or whether when you are reporting yes/no questions. It doesn't matter which you choose: Can you take care of Tommy for me? ~ I don't know yet whether / if I shall be able to look after Tommy during the Easter holidays or not. Is Paco still around? I wondered whether / if Paco had left the country as I hadn't seen him for some time. whether not if However, after prepositions, before to-infintives, inwhether…or… constructions and whenever we start a sentencewith the conjuntion, we have to use whether: Whether I'll get there in time for Henry's lecture, I don't know. I can't make up my mind whether to buy some new summer clothes now or wait until the prices go down.. There was a lot of discussion about whether Ringo should have his tongue pierced or not. Whether we go by bus or by train doesn't really matter. It's bound to be a slow journey. I'm going to spend all of granny's money on a new kitchenwhether you like it or not!

			if not when in 'conditional' sentences In 'conditional' sentences, we normally use if. If we are describing something which must happen first so that something else can occur, i.e. referring to a condition for something to happen, we have to use if, unless if means whenever. Consider these three conditional sentences below and then scroll back to the very first examples to remind yourself about if meaning whenever: I'll help you landscape the garden, if I can get off work for a couple of weeks. Don't take any chances. What would you do if you lost your job? If my dad had been alive, he would've sorted it all out for you in a matter of days.

From Different sources

When or if? 
We use when for things that are certain to happen in the future: 

I’ll buy you a pair of gloves when I go shopping this afternoon. 
I’ll give you a ring when I get home from school. 
Note that although the reference is clearly to the future, we use the present tense in the when-clause. 

We use if for things that may happen and which we are not certain about: 

If I decide to come to London this year, I’ll come and visit you. 

I’m going to call the police if she’s not back within the hour. 

If you make the salads, I’ll prepare the barbecue. 
In all of these examples, we are talking about future conditions and whether we use when or if depends upon the certainty of things happening. 

However, when and if are interchangeable when we are talking about general conditions that always apply when if means almost the same as whenever. Compare the following: 

I keep the air-conditioning on at night if the temperature goes above 30 degrees. 

I keep the air-conditioning on at night whenever / when the temperature goes above 30 degrees. 

If the green flag is flying, it’s quite safe to swim here 
You can swim here whenever / when / provided the green flag is flying. 

if vs. when

if and when are interchangeable when the statement of the conditional clause is a fact or a general issue (also known as zero conditonal)
If you heat ice, it melts.
When you heat ice, it melts.

if is used for something that, according to the speaker, might happen.
We can spend the afternoon on the beach if the weather is fine.

when is used for something that, according to the speaker, will happen.
I will clean up the kitchen right away when I'm back from work.

in case vs. if

in case of can be used to shorten an if-clause as shown below:
If there is a fire, leave the room.     In case of fire, leave the room.

While if expresses a condition (1), in case is used to express a possibility (2).
(1)     I need painkillers if I'm in severe pain.
(2)     I need painkillers in case I'm in severe pain.

The expression just in case is used pretty much the same way.
I got you a pizza just in case you were hungry.
(I don't know whether you are hungry.)

Rather Than Vs Instead of

christiancryan : MGMAT
There IS a crucial difference between "rather than" and "instead of" that you should know. "Rather than" is a conjunction and so can be followed by basically anything, whereas "instead of" is a (complex) preposition -- and a preposition should be followed only by a noun. 

Now, the noun can be an "-ing" verb, known as a gerund. So, the sentences you quote are not grammatically wrong in this regard. However, the GMAT seems to prefer "rather than" in comparisons of verbs, because the parallelism is clearest: 

(1) "I ski rather than snowboard." -- Correct. 
(2) "I ski instead of snowboarding." -- Correct, but a 'little' less parallel, so (1) is slightly preferable. The GMAT probably won't test this point in isolation, though  so we're going to revise the question. 

You can also use "rather than" to compare phrases or clauses. In that context, "instead of" is absolutely wrong, even though it's heard in spoken English: 
(3) "I went in the cellar rather than in the attic." -- Correct. 
(4) "I went in the cellar instead of in the attic." -- INCORRECT although this 'sounds' normal to me, to be honest! (That's why you have to retrain your ear -- it's not always grammatically right!) 
(5) "I went in the cellar instead of the attic." -- Also correct. No difference in preference between (3) and (5). 

As for the meaning of the two expressions -- to my ear, they have slightly different connotations or nuances ("instead of" sounds more like an actual replacement to me than "rather than," which is somehow softer), but the GMAT doesn't seem to test that connotational difference. 

So -- when in doubt, go with "rather than"! 

RonPurewal : ( MGMAT)

You are right to want to split hairs here, as there are often subtle differences in accepted usage of similar expressions. However, 'rather than' and 'instead of' are pretty much interchangeable. If there are any differences in their usage, then such differences will undoubtedly boil down to writers' personal preferences. 
So, in short: don't worry about it. And if you see a 'split' between these two expressions in a multiple-choice problem, then the split is probably there to deflect your attention away from the splits that actually matter (those sneaky @(*%^@(&*'s!!)


http://www.manhattangmat.com/forums/questions-involving-comparison-a-huge-confusion-t1593.html


StaceyKoprince ( MGMAT)
Keys to remember for this test: 

Both "X rather than Y" and "X instead of Y" will require parallelism for X and Y. 

Instead OF begins a prepositional phrase, so Y will have to be in the form of a noun. Since parallelism is required, so will X. 
Rather THAN can be followed by verbs or nouns - it's more flexible. 

Solely as a result of that, "rather than" is more commonly right than "instead of" ON THE GMAT because there are more errors we can build into "instead of" options. If you have to guess, choose an option that uses "rather than." But, ideally, check the rest of the sentence (and don't forget about that parallelism issue!). 

Note that this also means they won't give you two choices that are otherwise completely grammatically correct and use nouns for X and Y - and for which one uses "rather than" and the other uses "instead of." There'd be no way to choose - they'd both be right. (Yet another reason why "rather than" tends to be right on the GMAT more often than "instead of.")


Example :

1.     Hoping the customers would not carelessly throw too many of them away, Bob's Java Hut recently began supplying metal tableware instead of plastic. 

A) Hoping the customers would not carelessly throw too many of them away, Bob's Java Hut recently began supplying metal tableware instead of plastic 
B) Hoping the customers would not carelessly throw too many of it away, Bob's Java Hut recently began supplying metal tableware instead of plastic 
C) Hoping the customers would not carelessly throw too much of them away, Bob's Java Hut recently began supplying metal tableware instead of plastic 
D) Hoping the customers would not carelessly throw too much of it away, Bob's Java Hut recently began supplying metal tableware instead of plastic 

      E) Hoping the customers would not carelessly throw too much of it away, metal tableware has begun to be supplied recently instead of plastic at Bob's Java Hut

 OA : D



2. Rather than accept the conventional wisdom that the earth was flat, Christopher Columbus was sent by the king and queen of Spain to see if he could reach India by traveling west.


A. Rather than accept the conventional wisdom that the earth was flat, Christopher Columbus was sent by the king and queen of Spain to see if he could reach India by sailing west.
B. Rather than accepting the conventional wisdom that the earth was flat, Christopher Columbus was sent by the king and queen of Spain to see if he could reach India by sailing west.
C. Instead of accepting the conventional wisdom that the earth was flat, Christopher Columbus sailed west to see whether he could reach India, having been sent by the king and queen of Spain.
D. Rather than accept the conventional wisdom that the earth was flat, Christopher Columbus sailed west to see whether he could reach India, having been sent by the king and queen of Spain.
E. Instead of accepting the conventional wisdom that the earth was flat, Christopher Columbus was sent by the king and queen of Spain to sail west to see if he could reach India.

OA : D

Appositive Vs. Absolute phrase

Appositive : 

The definition: An appositive is a modifier; it is placed next to some other word or phrase, and it is a synonym of or possible replacement for that other word or phrase.

Most of the time, appositives are used as noun modifiers and contain nouns themselves, but they can also be adverbial modifiers.

Non-essential appositives must be set off from the core of the sentence by punctuation marks; essential appositives are not set off from the rest of the sentence by punctuation marks.

Appositives can be placed before or after the word or phrase they modify, and they can modify an entire phrase rather than just a single word.

If the appositive is CONCRETE, it MUST modify preceding noun.

example : I went to bar with Mr. Smith, a consultant from Fresno. 

If the appositive is ABSTRACT, it CAN whole idea of the modify preceding clause. BUT if the preceding noun is also abstraction then these can also modify the preceding noun.

Example: I went to bar with Mr. Smith, an outing that was far more fun than staying at work. 

Example: On Sunday our company will hold it annual field day, an outing at which employees drink beer, softball, and relax.

Concrete : is a description use to describe items/people/things that you can actually detect with your sences. Example : things you can touch, hear, hold on you hand, feel it , smell it etc.

Abstract: is a description use to describe items / ideas that you can not actually detect with your sences. Example : relationship, situation etc.

========================
Appositive Vs. Absolute phrase
Appositives rename noun phrases and are usually placed beside what they rename .
The following example shows a noun phrase in apposition to another:
The lady, our president, spoke out against racism.

"Our president" renames the subject "the lady" and so is
in apposition to it.

Absolute phrases are made of nouns or pronouns followed by a participle and any modifiers of the noun or pronoun. Absolute phrases contain a subject (unlike participial phrases), and no predicate. They serve to modify an entire sentence : A group of words that modifies an independent clause as a whole.

Joan looked nervous, her fears creeping up on her.
noun/subject: her fears
participle: creeping
modifier: up on her
absolute phrase: her fears creeping up on her

Tom paled when he came home, his mother standing in the
doorway.
noun/subject: his mother
participle: standing
modifier: in the doorway
absolute phrase: his mother standing in the doorway


=== Experts =========================
You need to use meaning to distinguish between appositives and absolute phrases. Since absolute phrases are modifiers, they will usually contain a different kind of information than an appositive. In sentence 1, "his arm in pain" modifies Guillermo. It wouldn't make sense to say that Guillermo and "his arm in pain" are the same thing. (Note also that the sentence begins with "His arm." It would not be correct to place the name Guillermo both before and after the phrase.)

In the appositive example, the coach is also an old classmate. Since it makes sense for a coach to be the same as an old classmate, we can see that this is an appositive. 

The second example of an absolute phrase ("The car fell into the lake, the cold water filling the compartment.") is a bit more tricky. It is possible for "the lake" and "the cold water filling the compartment" to be the same thing, so we could interpret this as an appositive. However, since a lake is something everyone should be familiar with, it makes more sense to read this as an absolute phrase. The second portion of the sentence does not modify the word "lake," but rather describes the result of the event mentioned in the first half of the sentence.

To sum up, you know you are dealing with an appositive when it seems logical to think of the two adjacent nouns as identical. If the noun in the modifying phrase is *doing* something ("He stepped out of the car, his leg bleeding badly."), you are probably dealing with an absolute phrase.

Number Vs Amount

Number : Use with Countable Noun.  Example: number, few , fewer, many
Amount: Use with Uncountable noun. Example : quantity, less, little, much

The administration has increased the number of fines for mining safety violations as part of their campaign to protect miners.
has increased the number of fines for mining safety violations as part of their
have increased the number of fines for mining safety violations as part of their
has increased the number of fines for mining safety violations as part of its
has increased the amount of fines for mining safety violations as part of its
have increased the amount of fines for mining safety violations as part of their

OA : C