relationship vs similarity

relationship

noun
  • Connection or association; the condition of being related. 

  • The level or degree of affinity between keys, chords and tones. 

  • The links between the x-values and y-values of ordered pairs of numbers especially coordinates. 

  • Kinship; being related by blood or marriage. 

  • A romantic or sexual involvement. 

  • A way in which two or more people behave and are involved with each other 

similarity

noun
  • The relation of sharing properties. 

  • A transformation that preserves angles and the ratios of distances 

  • The property of two matrices being similar. 

  • Closeness of appearance to something else. 

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