noun (n)

• the act of specializing; making something suitable for a special purpose(noun.act)

  Synonym:
  specialisation
  

  source: wordnet30
• the special line of work you have adopted as your career(noun.act)

  Example:
  His specialization is gastroenterology.
  

  Synonym:
  specialisation, specialism, speciality, specialty
  

  source: wordnet30
• (biology) the structural adaptation of some body part for a particular function(noun.process)

  Synonym:
  differentiation, specialisation
  

  source: wordnet30
• The act of specializing, or the state of being spezialized.(noun)

  source: webster1913