What Is an Existential Sentence in English Grammar?

In English grammar, an existential sentence is a sentence that asserts the existence or nonexistence of something. For this purpose, English relies on constructions introduced by There (known as the "existential there").

The verb most often used in existential sentences is a form of be, though other verbs (e.g., exist, occur) may follow the existential there.

Examples and Observations

• "There is always some madness in love. But there is also always some reason in madness."
  (Friedrich Nietzsche, "On Reading and Writing," Thus Spoke Zarathustra)
• "In the great green room,
  There was a telephone
  And a red balloon
  And a picture of--
  The cow jumping over the moon."
  (Margaret Wise Brown, Goodnight, Moon, 1947)
• "By using there as a dummy subject, the writer or speaker can delay introducing the real subject of the sentence. There is called a dummy subject, dumS, because it has no meaning in itself--its function is to put the real subject in a more prominent position."
  (Sara Thorne, Mastering Advanced English Language. Palgrave Macmillan, 2008)
• "Rick, there are many exit visas sold in this café."
  (Captain Renault, Casablanca)
• The term existential sentence is an attempt to capture the meaning conveyed by the following type of construction:
  There's a strange cat in the garden
  There were lots of people in town.
  There weren't any apples on the tree.
  There appeared a bright star in the sky. The word there comes first . . .. It is then followed by the simple present or past tense of be, or a small range of 'presentational' verbs, such as: appear, arise, ascend, come, emerge, erupt, exist, float, occur, spring up, stand. The noun phrase following the verb is usually indefinite, as shown by such words as a and any...
  "What the there construction does is highlight a clause as a whole, presenting it to the listener or reader as if everything in it is a new piece of information. It gives the entire clause a fresh status. In this respect, existential sentences are very different from the other ways of varying information structure, which focus on individual elements inside a clause."
  (David Crystal, Making Sense of Grammar. Pearson Longman, 2004)

Subject-Verb Agreement With Existential ​There

"[T]he normal rules of subject-verb agreement do not apply to there constructions since a singular verb form is frequently used even when the term following be is plural:

(7) There's some people that I'd like you to meet.

(8) There is some things I can't resist

(9) There happens to be only two apples left

(10) A: Who is there who could help her?
B: Well there's always you
B': *Well there are always you

The examples above show that agreement in English existentials is rather erratic and consistent with any of the following three analyses: (i) agreement is determined by the term following be; (ii) agreement is determined by there; (iii) there may be no controller of agreement at all . . .. In any case, agreement cannot be taken as the decisive criterion in determining which of the two candidates has Subject function." (Dubravko Kučanda, "On the Subject of Existential There." Working with Functional Grammar: Descriptive and Computational Applications, ed. by Michael Hannay and Elseline Vester. Foris, 1990)