noun (n)

• the union of diverse things into one body or form or group; the growing together of parts(noun.act)

  Synonym:
  coalescency, coalition, concretion, conglutination
  

  source: wordnet30
• The act or state of growing together, as similar parts; the act of uniting by natural affinity or attraction; the state of being united; union; concretion.(noun)

  source: webster1913