quick grammar ques.?

Question

A new bulletproof material has been developed, that is very lightweight.



is placing a comma there incorrect? i think so.
if you respond, please name a grammatical rule as to why you think it is correct/incorrect.

Answer 1

Yes, the comma is used incorrectly. Reason: trailing restrictive clauses are not set off by a comma. In the discussion below, look for [rule] preceding a grammatical rule I'm about to articulate.

Introduction:
"You are about to participate in a great adventure. You are about to experience the awe and mystery that reaches from the inner mind to ... The Outer Limits." -- The Control Voice, circa 1963.

First of all, the relative adjective clause 'that is very lightweight' modifies the noun 'material'. Thus, [rule] the relative adjective clause must follow its noun, rather than dangle past the verb 'developed', at the end of the sentence.

Second, the two adjectives, 'new' and 'bulletproof', equally and coordinately modify the noun 'material'. Therefore, [rule] the two equal, coordinate adjectives must be separated by a comma.

Now we have the still incorrect sentence,

A new, bulletproof material, that is very lightweight, has been developed.

Next, let's discuss the relative pronouns 'that' and 'which', the only two relative pronouns that are used with things (as opposed to 'who', 'whom' and 'whose', the relative pronouns that are used with people.) Moreover, we'll discuss using a restrictive relative pronoun to refer to one among many, as well as using a nonrestrictive relative pronoun to discuss parenthetical details of the one item under discussion.

In conjunction with using the relative pronoun 'that', setting off the relative clause with commas is incorrect, because the relative pronoun 'that' is restrictive. [rule] A restrictive clause is never set off by commas. [rule] Only a nonrestrictive clause is set off by commas. [rule] The only nonrestrictive relative pronoun used to refer to things is 'which'.

(And for premium, high-test, compulsively hair-splitting discussion, we note that some use 'which' for either restrictive or nonrestrictive characterization while they let commas denote nonrestriction and the lack of commas denote restriction. Others, like me, use 'which' and commas for nonrestriction versus 'that' and the absence of commas for restriction. I wish I could remember the book written about 20 - 30 years ago, in which a panel of experts debated and voted on points of English like this one.)

In our case, the restrictive relative pronoun 'that' connotes that all material under discussion is new and bulletproof, and we're restricting our news to that new, bulletproof material that is singularly lightweight among other new, bulletproof materials.

Thus, if we're discussing the lightweight, new, bulletproof material among other new, bulletproof materials, it is correct to write either (depending on stylistic choice, above, neither one of which is universally considered to be correct):

A new, bulletproof material which is very lightweight has been developed.

or

A new, bulletproof material that is very lightweight has been developed.

In contrast, let's suppose that exactly one new, bulletproof material has been developed, and it just happens to be lightweight. This is the nonrestrictive case. [rule] We must use the relative pronoun 'which', and we must set off the nonrestrictive relative clause with commas. The only correct sentence connoting nonrestriction is:

A new, bulletproof material, which is very lightweight, has been developed.

Please vote: Did this help?

Answer 2

There is no need for a comma because you arent separating ideas.
the very lightweight is description not another idea.
I would reword the sentence though, it sounds a little awkward as it currently is.
A new lightweight bulletproof material has been developed.
A new bulletproof material that is lightweight has been developed.

Answer 3

No comma needed. Perhaps it could be phrased as " A new bulletproof material has been developed which is very lightweight.".

Answer 4

No comma needed because the comma basically divides the sentence into two. Look at the sentence and where the comma is. Are there two complete sentences completing a thought? If not, then no comma is needed.

I.E. 1. My brother is going to miss gym, because he broke his
arm.
2. I feel sick, but I am going to the mall later.

Breakdown: 1. My brother is going to miss gym.
He broke his arm.

2. I feel sick.
I am going to the mall later.

Two complete thoughts. See?
Hope that helped.

Answer 5

The sentence is ambiguous. It should be re-structured as follows: A new bulletproof material, that is very lightweight, has been developed.
OR/
A new lightweight, bulletproof material has been developed.

Answer 6

It is incorrect.
I am not sure what you mean by 'rule' but by separating it like that, you change the meaning. All of it together is part of one statement.

Answer 7

if it doesn't sound "right" it probably isn't just reword the sentence