Why ‘is’ is not really a verb

In grammar, we call ‘to be’ a verb, or use the term ‘linking verb’. ‘To be’ is certainly something very similar to a verb: it forms the same sorts of constructions with the same moods, tenses (past, present, future) and aspects (perfect, continuous, habitual); it often acts as an auxiliary verb in constructions with other main verbs; it can be an intransitive verb in its own right (as a synonym for ‘exist’); but in its typical usage it is distinctly different from other verbs in certain ways and deserves to be thought of as something slightly different from a verb. In Linguistics, the label given to ‘to be’ in its classic usage (“dinner is ready”) is the Copula.

Arguments and Complements

True verbs may or may not have nouns or clauses they interact with, which in Linguistics are called arguments. The most well-known argument of a verb is the Object. Other arguments can include the Indirect Object, the Result State (an adjective), a location phrase, or a dependent prepositional phrase (a prepositional phrase required by a particular verb). However, ‘to be’, the Copula, doesn’t have arguments, it has complements, the technical term applied to them is Predicative Complement (I’ll just use the term Complement, with a capital letter, as a proper noun).

‘To be’ can take four types of Complement:

  • A noun phrase:*
           “An apple is a fruit.”
  • An adjective phrase:
           “That apple is totally rotten.
  • A location phrase:
           “Your guests are here.”
  • A prepositional phrase:
           “The children are at the beach.”

[* In Linguistics and grammar, a phrase can consist of a single word. For example, a single pronoun is still a noun phrase.]


I’ve described elsewhere the syntactic movement that occurs to cause adverbs to adopt the positions they do in English grammar, which is somewhat linguistic and technical, so I won’t discuss it here. The important thing to note, however, is that ‘to be’ behaves differently from a true verb, especially when it is in a single-word construction (i.e. one without modal or auxiliary verbs).

In a verbal construction, the natural position for most adverbs* is after the modal or first auxiliary (if there is one), but before the main verb; and an adverb can only appear between the verb and its main arguments (e.g. the Object) in very exceptional circumstances.

[* Adverb position is quite irregular and some adverbs strongly prefer some positions more than others.]

For example, with single-word verb constructions:
        “She always      ate        healthy food.
                         adverb     main verb          Object
is grammatical, but:
       She ate             always   healthy food.
                     main verb      adverb                 Object
is definitely not.

With single-word ‘to be’ verb:
       She was    always     healthy.
                    ‘to be’       adverb         Complement
       She    always     was          healthy.
                         adverb       main verb      Complement
are both equally grammatical. However, with a single-word ‘to be’ construction, the most common natural adverb position is after ‘to be’:
       She was     always    healthy.
                    ‘to be’       adverb        Complement.

For a multi-word verbal construction, the natural position of the adverb is after the Modal or first Auxiliary:
       She     would     always     have       eaten          healthy food.
                          modal            adverb          auxiliary      main verb         Object
This is the same for ‘to be’ constructions with modals or auxiliaries:
       She has         always    been     healthy.
                      auxiliary    adverb         ‘to be’         Complement

Adverb placement with ‘to be’ is much more subtle than with verbs. ‘To be’ constructions with Modals or auxiliaries, as noted above, are essentially the same as those with verbs, but single-word to be constructions are quite different, with a different natural position for the adverb and more flexibility in where it can be placed. Some usages sound better than others (which suggests much more complex and varied syntactic movement).

One interesting thing to note (for very advanced speakers or readers interested in Linguistics) is that the natural position varies in single-word constructions depending on whether one is using the present tense or past tense:
       She always   was     healthy.
                    adverb        ‘to be’      Complement
sounds better than:
       She   always   is       healthy.
                       adverb       ‘to be’     Complement
In the present tense, it sounds much better to say:
       She   is        always    healthy.
                       ‘to be’    adverb         Complement

In this way, ‘to be’ in the simple present tense (am, are, is) acts like an auxiliary verb with no main verb, but ‘was’ can either adopt the auxiliary or main verb position.* In other words, in the past tense, the adverb can appear on either side of was, but in the present tense it sounds better if it follows was.

[* If you understood the article on the Verb Phrase, this is because the present tense of ‘to be’ is inflected for person and number (am, is, are), but ‘was’ is not, so there is a much stronger pull to the Head of Inflect Phrase for the present tense.]

Thus, in terms of sentence structure, ‘to be’ has Complements and not arguments, and adverb placement is more varied than with true verbs.


‘To be’ also acts differently to verbs in conditionals,* with respect to ‘unreality’.

[* if you are interested in the details of conditionals and unreality there is a long article here.]

In unreal conditionals, in standard less-formal English, unreality is expressed by a ‘step back in time’. For example:
       If I knew the answer, I would tell you,
uses the past tense to describe the unreal present; and:
       If I had known the answer, I would have told you,
uses the past perfect to express the past.

       If I was rich I would be happy,
is not grammatical in standard English (although it is widely used in casual English); the formal (or subjunctive) form should always be used with ‘to be’:
       If I were rich, I would be happy.

As well as this, it is typically enough in standard English just to use the ‘were’ form. We are far less concerned about ‘stepping back’ instances of ‘to be’ into the past-perfect. For example, with a verb in the unreal past in standard English, we should say:
       If I had seen it, I would have told you,
but, when talking about the unreal past:
       If I saw it, I would have told you,
sounds very casual.
However, with ‘to be’:
       If I had been there, I would have seen it,
       If I were there, I would have seen it,
are both equally acceptable. We only feel the need to use the past perfect if there might be confusion as to whether the ‘to be’ state still exists. In other words, if there were some confusion about whether I were still there in the above example, I might use “if I had been there,” but otherwise, “if I were there” is fine.

To summarise, in conditionals, unlike with true verbs, we see that ‘to be’ is expressed in the subjunctive mood and never in the simple past, at least in standard English, and the ‘step back in time’ is often not applied.


Full Subject-Object inversions with verbs are very rare in English. They sound extremely stylistic and very old fashioned. For example:
       The dragon      slew      he,
           Object                       verb          Subject
where ‘he’ (obviously) is the Subject, sounds so old-fashioned it is positively Mediaeval. However, when ‘to be’ is used, inversions are a lot more common. For example:
       Happy            is         the man who loves his work,
          Complement        ‘to be’       Subject
sounds a little old-fashioned and stylistic, but is still quite acceptable in modern English.

When ‘to be’ has a prepositional phrase or a location as a Complement, such Subject-Complement inversions are actually very common, as in:
       On the bench          are       some apples.
          prepositional phrase      ‘to be’       Subject
       Here                     are         your notes.
          location phrase           ‘to be’         Subject
In fact, these types of Subject-Complement inversions, with location phrases or prepositional phrases, are probably as common as the non-inverted forms.


So we all call ‘to be’ a verb because it is very similar to a verb, but it is useful to be aware that, when you are learning English, ‘to be’ – in its role linking nouns and their Predicative Complements – has many rules all of its own. Sentences with a single-word form of ‘to be’ have different sentence ordering, with adverbs preferring different positions; unreal conditionals with ‘to be’ are different to those with true verbs – with were always replacing was in standard English, and with less need to apply a ‘step back in time; and Subject-Complement inversions, especially those involving prepositional phrases or location phrases, are very common, while Subject-Object inversions are extremely rare with true verbs.

You can think of it as the Copula, a verb, a linking verb, or just ‘to be’, but just be aware that it is not like any other verb.

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