Student or Learner
***** NOT A TEACHER *****
antigen, glycerol, glycogen and as you can see these words are also categorized as 'specialized' words. I'd say that by 'specialized' they mean that these words appear in specialist literature - that is, textbooks, academic articles and so forth. It's the equivalent of 'technical', a term which is used by the Longman Dictionary of Contemporary English - see antigen - Definition from Longman English Dictionary Online.