drowsy vs half-asleep

drowsy

adj
  • Inclined to drowse; heavy with sleepiness 

  • Causing someone to fall sleep or feel sleepy; lulling; soporific. 

  • Dull; stupid. 

  • Boring. 

half-asleep

adj
  • Showing signs of being asleep or very sleepy, as not demonstrating full energy or attention. 

How often have the words drowsy and half-asleep occurred in a corpus of books? (source: Google Ngram Viewer )