Definition of does verb in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.
Average household income is lower in the north than the south but this does not affect the performance of its primary schools.
Exist or Exists is a matter of past, present, and future with indirect context. Past: The file was not found. Did it ever exist? It never existed. Has been (existing) is a reference to previously existed and currently exists. Comparing the creation and modification time stamp indicates the file existed without change, for 17 days.
Neither is a correctly formed utterance. If you're asked: Does photographic memory exist? The shortest answer is simply "No." If you want to use a complete sentence, replace the subject with the pronoun it and add the dummy auxiliary do so you can negate it and omit the verb: No, it doesn't. I'm afraid that neither of the options you've given is correct.
That file doesn't exist. In any verb construction (auxiliaries + lexical verb) only the first is inflected for tense, person and number. In your example does is the first verb in the construction does exist. Auxiliary do always takes an infinitive (plain) form as its complement: exist.
word usage - “file doesn’t exist” or “file doesn’t exists” - English ...
If there exist..... is the subjunctive form of the verb (about which you will find hundreds of illustrations on the net). It's like saying: If there be another challenger, let him come forward. - a construction that has a somewhat poetic or theatrical ring.
The verb exist is stative and is not usually cast in the progressive form, except as an adjectival participle: it bears a "progressive" sense inherently. You are casting exist in the wrong tense: the teacher is referring not to the present existence of the phrase but to its past existence, before the students used it.