WordNet (r) 3.0 (2006):

specialisation
    n 1: (biology) the structural adaptation of some body part for a
         particular function; "cell differentiation in the
         developing embryo" [syn: specialization,
         specialisation, differentiation]
    2: the act of specializing; making something suitable for a
       special purpose [syn: specialization, specialisation]
    3: the special line of work you have adopted as your career;
       "his specialization is gastroenterology" [syn:
       specialization, specialisation, specialty,
       speciality, specialism]

The Free On-line Dictionary of Computing (30 December 2018):

specialisation

   A reduction in generality, usually for the sake of increased
   efficiency.  If a piece of code is specialised for certain
   values of certain variables (usually function arguments), this
   is known as "partial evaluation".  In a language with
   overloading (e.g. Haskell), an overloaded function might be
   specialised to a non-overloaded instance at compile-time if
   the types of its arguments are known.