cause
I
 /ˈkɑːz/  noun  ,  pl   caus·es
  1 [  count  ] : something or someone that produces an effect, result, or condition : something or someone that makes something happen or exist
   His symptoms had no apparent physical causes.
   She is the cause of all their problems.
   He died of/from natural causes. [=he died because of old age or an illness]
  — often + of
   The doctor determined the cause of death.
   The exact cause of the accident/fire is not known.
  2 : a reason for doing or feeling something
   [  noncount  ] The medicine was prescribed without good cause.
    — often + for
    There is some cause for concern. [=some reason to be concerned/worried]
   
   [  singular  ] Their marriage was a cause for celebration. see also probable cause
  3 [  count  ] : something (such as an organization, belief, idea, or goal) that a group or people support or fight for
   I can support a cause that means something to me.
   I'm willing to donate money as long as it's for a good/worthy cause.
  lost cause
   : a person or thing that is certain to fail
    She decided her acting career was a lost cause.
    I'm a lost cause when it comes to anything technical.
  make/find common cause
    formal   : to join together with someone in order to achieve a shared goal
    He has made common cause with political rivals to defeat the proposed new law.
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II
  verb  , causes, caused, caus·ing [  + obj  ]
  1 : to make (something) happen or exist : to be the cause of (something)
   He swerved and caused an accident.
   The flood caused great hardship.
   The illness is caused by a virus.
  2 : to make (someone) feel, have, or do something
   The flood caused the town great hardship.
   You caused us a lot of extra work.
  — often followed by to + verb
   His boss caused him to resign. [=his boss made him resign]
   His nervous behavior caused me to question his innocence.