additive vs summative

additive

adj
  • Pertaining to addition; that can be, or has been, added. 

  • Of or pertaining to genes (or the interaction etc. of such genes) which govern the same trait and whose effects work together on the phenotype. 

  • Pertaining to chemical addition. 

  • That is distributive over addition. 

  • Whose operator is identified as addition. 

noun
  • A substance added to another substance or product to produce specific properties in the combined substance. 

  • A word or phrase that adds something, such as also, even, or nor. 

summative

adj
  • Of, pertaining to, or produced by summation. 

  • Denoting forms of assessment used to quantify educational outcomes. 

How often have the words additive and summative occurred in a corpus of books? (source: Google Ngram Viewer )