erratic vs reliable

erratic

noun
  • A rock moved from one location to another, usually by a glacier. 

  • Anything that has erratic characteristics. 

adj
  • Deviating from normal opinions or actions; eccentric; odd. 

  • Unsteady, random; prone to unexpected changes; not consistent. 

reliable

adj
  • Suitable or fit to be relied on; worthy of dependence, reliance or trust; dependable, trustworthy 

  • Such that either a sent packet will reach its destination, even if it requires retransmission, or the sender will be told that it didn't 

noun
  • Something or someone reliable or dependable 

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