determinant

Adjective

• having the power or quality of deciding
  • the crucial experiment
    
  • cast the deciding vote
    
  • the determinative (or determinant) battle
    

Noun

• a square matrix used to solve simultaneous equations

• the site on the surface of an antigen molecule to which an antibody attaches itself

• a determining or causal element or factor
  • education is an important determinant of one's outlook on life
    

Related words

• Synonyms: 
  deciding(a) , determinative , determining(a) , antigenic determinant , epitope , determiner , determining factor , causal factor