The verb need is both used as an ordinary verb and as a modal verb
| 
ORDINARY VERB | 
MODAL VERB | 
| 
She
  needs a new car   
(need is followed by an object) 
She doesn’t need a new car 
Does she need a new car? | 
In
  the negative form 
She needn’t buy a new car 
(here there isn’t s at the third person) | 
| 
She needs to buy a new car 
(need followed by a verb) 
She
  doesn’t need to
  buy a new car 
Does
  she need to buy a
  new car? | |
| 
She needed to buy a new car 
She didn’t need to buy a new car | 
She needn’t have bought a
  new car  | 
| 
She will need to buy a new car 
She won’t need to buy a new
  car | |
| 
She has needed to buy a new car for
  long time | |
| 
My room needs cleaning 
My room doesn’t need
  cleaning | 
 
