The expressions Like and As are used to present comparison and are often tested against each other.
Correct usage of Like
When used to present comparison, like must be followed by a noun entity. This noun entity can be a single noun word or a noun phrase. The noun following like is compared to the subject of the main clause.
Simple Example 1
Like iron, mercury is a metal.
In the above-mentioned sentence, the word like has been used to present the comparison between two entities – iron and mercury. The two entities have been compared on the basis that they both are metal. Please note that in this sentence, the word like has been used by the single word noun entity iron and is logically and grammatically compared to the subject, a noun entity, mercury.
Official Sentence 1
Like embryonic germ cells, which are cells that develop early in the formation of the fetus and that later generate eggs or sperm, embryonic stem cells have the ability to develop into different kinds of body tissue. (OG 2020 Diagnostic Test#95, Choice B)
The above-mentioned is the official sentence with the correct answer choice. In this sentence, like has been used to compare embryonic germ cells and embryonic stem cells. They have been compared because both kinds of cells can develop into various types of body tissue.
The word Like is correctly followed by the noun entity embryonic germ cells and it logically and grammatically compared to the subject of the main clause embryonic stem cells.
Official Sentence 2
Going ahead without the presence of a definite plan for upcoming labor negotiations, like the firm had agreed last year to do, would surely have proven disastrous in the face of the skilled and resolute opposition involved this time. (OG VR 2020#249, SC89941.01, Choice C)
The above-mentioned sentence is incorrect because in this version of the sentence like is followed by a clause or an SV pair – the firm had agreed….
Correct usage of As
The word ‘as’ is also used to present comparison. But it is followed by either a clause (an SV pair) or a prepositional phrase.
Simple Example 2
As filmmakers showcase their talent through film festivals, musicians reach out to their audiences through musical festivals.
In the above-mentioned sentence, as has been used to present comparison between filmmakers and musicians. The two groups have been compared because both resort to some specific events to exhibit their talent. Please note that in this sentence, as is followed by a clause – filmmakers showcase….
Official Sentence 3
Ramón pointed out that food high in whole-grain fiber creates the energy we need to fight illnesses—as do vegetables and lean proteins. (OG 2020#827, SC41451.01)
Let’s first understand the meaning of this correct official sentence. The sentence says that according to a person named Ramón, food that are rich in whole-grain fiber produces the energy our bodies need to fight illnesses. Vegetables and lean protein also do the same.
Hence, the sentence presents a comparison between food high in whole-grain fiber and vegetables and lean protein. Both these food items have compared because they produce same kind of energy. Use of as presents logical comparison here and is correctly followed by the clause (SV pair) do vegetables and lean proteins.
Please note that in GMAT SC, the verb in the second part of the comparison appears before the subject. Hence, we see the usage of the verb do before its subject vegetables and lean proteins. Placing this verb after the subject will not change the intended comparison in the sentence.
A Notable fact – Like vs AS
Because while presenting comparison like is followed by a noun entity and as by a clause, it is a general perception that like is used to compare noun entities while as is used to compare actions. However, in some cases, they can be used interchangeably.
For example, Simple Example 1 can be written as: As is iron, mercury is a metal.
Official Sentence 4
Proponents of artificial intelligence say they will be able to make computers that can understand English and other human languages, recognize objects, and reason as an expert does—computers that will be used to diagnose equipment breakdowns, deciding whether to authorize a loan or other purposes such as these.
(A) as an expert does—computers that will be used to diagnose equipment breakdowns, deciding whether to authorize a loan or other purposes such as these
(B) as an expert does, which may be used for purposes such as diagnosing equipment breakdowns or deciding whether to authorize a loan
(C) like an expert—computers that will be used for such purposes as diagnosing equipment breakdowns or deciding whether to authorize a loan
(D) like an expert, the use of which would be for purposes like the diagnosis of equipment breakdowns or the decision whether or not a loan should be authorized
(E) like an expert, to be used to diagnose equipment breakdowns, deciding whether to authorize a loan or not, or the like . (OG VR 2017#297)
In the above-mentioned official sentence, none of the answer choices can be rejected on the basis of the usage of like vs. as because all the answer choices correctly use both these expressions. The sentence is an example of a scenario when like and as can be used interchangeably with the correct structures.
- Both like and as is used to present comparison.
- While presenting comparison, like must be followed by a noun entity.
- While presenting comparison, as must be followed by a clause or an SV pair.