autonomous vs spontaneous

autonomous

adj
  • Acting on one's own or independently; of a child, acting without being governed by parental or guardian rules. 

  • Self-governing. Intelligent, sentient, self-aware, thinking, feeling, governing independently. 

  • Used with no subject, indicating an unknown or unspecified agent; used in similar situations as the passive in English (the difference being that the theme in the English passive construction is the subject, while in the Celtic autonomous construction the theme is the object and there is no subject). 

spontaneous

adj
  • Controlled and directed internally; self-active; spontaneous movement characteristic of living things. 

  • Sudden, without warning. 

  • Random. 

  • Done by one's own free choice, or without planning. 

  • Produced without being planted or without human cultivation or labor. 

  • Arising from a momentary impulse. 

  • Self-generated; happening without any apparent external cause. 

  • Proceeding from natural feeling or native tendency without external or conscious constraint. 

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