acknowledge vs be appreciative

acknowledge

verb
  • To own as genuine or valid; to assent to (a legal instrument) to give it validity; to avow or admit in legal form. 

  • To own or recognize in a particular quality, character or relationship; to admit the claims or authority of; to give recognition to. 

  • To be grateful of (e.g. a benefit or a favour) 

  • To admit the knowledge of; to recognize as a fact or truth; to declare one's belief in 

  • To report (the receipt of a message to its sender). 

be appreciative

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