An ELT Glossary : Particle / Infinitive particle / Negative particle

The usual definition of particle is that it is a word that does not clearly belong to any other word class - though the expression is also used for the type of adverb particle found in phrasal and phrasal prepositional verbs.

English has two such particles :

1. The infinitive particle

The infinitive particle is to. It precedes the infinitive and is used :
  • When the infinitive is the subject or object of the sentence : To lie won't help.
  • When it's the complement of the subject/object, or of an adjective : The idea is to leave on Thursday; It's impossible to go
  • As object after a wide range of catenative verbs - eg  I forgot to tell you: I want to see that film; I hope to know more soon.
  • As an appositive :  His dream, to visit Australia, was never realised.
  • As a non-finite clause : The next person to leave was John

2. The negative particle

The negative particle is not. It can be used to negate : 
  • finite verb forms, when it is usually attached to the  operator, and may be contracted to n't : I can't see anything; He hasn't arrived yet 
  • finite verb forms used as main verbs : this is mainly restricted to the verb Be - He isn't here - but sometimes occurs with with Have. particularly in fixed expressions : I haven't the foggiest idea. Using it with main verbs in other contexts may give the sense of a formal or  archaic style: Fear not! ; I decided I hadn't the time. 
  • non-finite verb forms, when it precedes the verb : She chose not to go; Not to reply would be rude: Not knowing about it, I didn't go
  • other word classes, when it again precedes the item it negates : Not many people know this; He spoke not French but German; Not unnaturally, he wanted to see her.

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