"This is allowed", is this passive voice?

• This is allowed.

Is the verb "is" a linking verb, or is this passive construction? Is there a difference? How does one tell?

Let's directly address your question, which is asking: How is the verb "is" being used in that example sentence?

For the OP's example, this boils down to whether to treat the word "allowed" as a verb or as an adjective. If the word "allowed" is a verb, then it is a past-participle verb form in a clause with passive voice. If it is an adjective, then the clause has active voice.

I think that reasonable arguments can be made for both the verbal interpretation and for the adjectival interpretation for your example. (In general: the context might often prefer one interpretation over the other.)

LONG VERSION: First, a little background info related to the verb "BE". In today's English, the verb "BE" has at least six major uses:

1. copular BE -- "She was a lawyer."
2. progressive BE -- "She was sleeping peacefully."
3. passive BE -- "They were seen by the security guard."
4. quasi-modal BE -- "You are not to tell anyone."
5. motional BE -- "She has been to Paris twice already."
6. lexical BE --"Why don't you be more tolerant?"

Your question involves the usages: "copular BE" vs "passive BE".

(NOTE: Above examples and info borrowed from 2002 CGEL, page 113.)

For clauses structured like yours, usually the surrounding context is what decides which interpretation is preferred or expected. But since we don't have the context, we'll have to just look at the clause in isolation and see what sort of diagnostic tools can be used to support a copular BE interpretation (adjectival "allowed") or a passive BE interpretation (verbal passive "allowed").

For verbal passive: Two common diagnostic tests are:

1. to see if an agentive by-phrase can be inserted into the example without significantly altering the meaning (also popularly known as the "by zombies" test),

2. to see if there is a somewhat similar active version for that example.

And, for "This is allowed", it seems that we can do exactly that for both:

• This is allowed by the current authorities.

• The current authorities allow this.

So, it seems that, at least a verbal passive interpretation is possible here.

Now, let's if there are some diagnostic tests for the copular BE interpretation, which is the same as the adjective "allowed" interpretation.

For adjective: Some common diagnostic tests are:

1. to see if the words "too" or "very" can be inserted without significantly changing the meaning,

2. to see if the verb "BE" can be replaced with verbs like "SEEM, APPEAR, LOOK, REMAIN".

The first diagnostic test doesn't seem to help:

• *This is very allowed. -- [non-standard or unacceptable, imo]

while the second test might be okay, or maybe not:

• This seems allowed.

There are many diagnostic tools that can help in this issue of "participle as verb-form vs participial adjective". For instance: complementation test, occurrences with "seem" test, modification by "very" or "too" test. (CGEL pages 78-9)

Also, in general, a dynamic situation will necessarily disallow the adjectival interpretation; but a stative situation will not necessarily disallow a verbal passive interpretation. Even then, some clauses can mislead: for "It was magnetized" can support both a verbal passive and an adjectival interpretation, while "It became magnetized" supports only the adjectival one (CGEL pages 1436-9). On CGEL page 1437:

Dynamic vs stative

Adjectival passives always have a stative interpretation. The clearest contrasts are between verbal and adjectival passives that differ as to whether they are interpreted dynamically or statively:

[36]

• i. They were injured when the platform they were standing on collapsed. -- [verbal]

• ii. She is injured and will have to miss the next two matches. -- [adjectival]

Similarly, the obvious ambiguities are those that allow either a dynamic or a stative interpretation, such as They were injured on its own, They were married (=[32.iii], The window was broken, and so on.

It must be emphasized, however, that adjectival and verbal passives cannot be distinguished simply by asking whether the interpretation is stative or dynamic -- it is for this reason that we have not included this among the tests for adjectival status. . . .

In conclusion: I guess the preferred interpretation for your example "This is allowed" will probably depend on the surrounding context. But it does seem to be easier to find supporting info for the verbal passive interpretation than for the adjectival one.

Note: If a past-participle shaped word is commonly used as an adjective, then dictionaries might add that word as an adjective entry--as an attributive adjective and/or a predicative adjective, depending on how it is syntactically used.

Aside: Dictionaries are sometimes looked into for an answer, though of course they are dictionaries and not a grammar source like a reference grammar. But they can sometimes be helpful, somewhat. I had done a very quick look into a few free online dictionaries, and they commonly have the verb usage, and maybe one might mention an attributive adjective usage, but in the dictionaries I've quickly looked at, they don't seem to provide a predicative adjective example-- hopefully the better dictionaries do exactly that (OED?).

Of course, this is a grammar issue (syntax), and so, it's probably better to try and rely on vetted grammar sources, such a reference grammar, than rely on dictionaries (even if it is the OED), especially not on free online dictionaries. A good vetted grammar source is the 2002 reference grammar by Huddleston and Pullum et al., The Cambridge Grammar of the English Language (CGEL).

= = = = = PERHAPS SLIGHTLY OFF-TOPIC = = = = =

• This is allowed.

Is the verb "is" a linking verb, or is this passive construction? Is there a difference? How does one tell?

An excerpt from an online dictionary has come up in this discussion, and so, let's see what it says. The excerpt is from The Free Dictionary for their entry "past participle": http://www.thefreedictionary.com/past+participle

past participle n.

• A verb form indicating past or completed action or time that is used as a verbal adjective in phrases such as baked beans and finished work and with auxiliaries to form the passive voice or perfect and pluperfect tenses in constructions such as She had baked the beans and The work was finished. Also called perfect participle.

Let's see what information we can get from it that is related to the OP's example:

• It says that a past participle is "A verb form . . ."

• "[a verb form] that is used as a verbal adjective in phrases such as baked beans and finished work"

• "and [that is used] with auxiliaries to form the passive voice or perfect and pluperfect tenses in constructions such as She had baked the beans and The work was finished."

Now, in that last bullet, the examples were given in a different order than I'd have expected. But I'd think it is obvious that "She had baked the beans" is an example of what they call the "perfect/pluperfect tense", and that "The work was finished" is an example of their "passive voice".

Let's look at another part of that excerpt, and see what it seems to be saying: "[a verb form] that is used as a verbal adjective in phrases such as baked beans and finished work." Here, the words "baked" and "finished" are being used as attributive modifiers in the noun phrases "baked beans" and "finished work". Many adjectives are used that way, as attributive modifiers of a noun.

But the OP's example--"This is allowed"--is a clause, not a noun phrase, and so, the OP's example is similar to that dictionary's example "The work was finished", which was their example of passive voice.

So, it seems that that dictionary's excerpt can be used to support the argument that the OP's example has (at least) a passive voice interpretation.

CAVEAT: Though, I will agree that the dictionary's text was sloppily done, and that it could possibly be mis-parsed if the reader didn't already know the answer to begin with. (For I can see a way that a mis-reading could be forced.)

It's either.

Both constructions are grammatical, and in sentences where allowed is coordinated with an adjective:

this is allowed but unadvisable,

it is hard not to read allowed as being an adjective and is as a linking verb. If you introduce an agent:

this is allowed by the authorities,

it is hard not to read is allowed as being a verb in the passive voice.

EDIT:

One way to see that you have to allow both possibilities is by looking at related sentences. You can start with a sentence where allowed is clearly an adjective:

the allowed colors are gray, blue, and black,

and alter it to get

gray, blue, and black are allowed.

Similarly, you can start with a sentence where allows is clearly a verb:

official policy allows gray, blue, and black,

and alter it to get

gray, blue, and black are allowed (by official policy).

The final sentence from both transformations is the same, and both transformations are almost always allowed by English grammar. If you claim that allowed must be either an adjective or a verb in the final sentence, then you are denying the validity of one of these transformations, and you need to explain why it is invalid in this case.