Grammar Reference
We use indefinite pronouns to refer to people, things or places without saying exactly who or what they are.
Compare:
| 
       anybody  | 
    
       anything  | 
    
       anywhere  | 
  
| 
       everybody  | 
    
       everything  | 
    
       everywhere  | 
  
| 
       nobody  | 
    
       nothing  | 
    
       nowhere  | 
  
| 
       somebody  | 
    
       something  | 
    
       somewhere  | 
  
Note:  
  anyone = anybody
  everyone = everybody
  no one = nobody
  someone = somebody
No one is written as two words.
When an indefinite pronoun is the subject it is followed by a singular verb.
Indefinite pronouns are singular, but to refer back to them we use plural pronouns, e.g. they, their, themselves, etc.