clustering vs heed

clustering

adj
  • Forming a cluster. 

noun
  • The undesirable contiguous grouping of elements in a hash table. 

  • A grouping of a number of similar things. 

  • A prewriting technique consisting of writing ideas down on a sheet of paper around a central idea within a circle, with the related ideas radially joined to the circle using rays. 

  • The grouping of a population based on ethnicity, economics or religion. 

heed

verb
  • To mind; to regard with care; to take notice of; to attend to; to observe. 

noun
  • Careful attention. 

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