Conflicting Words

What unique feature do the following words share?

FRIEND, FEAST, THERE, THOROUGH, FLIGHT, WONDERFUL, RESIGN, ENDURING, PEST, COVERT

Each of these words contains its antonym as a sub-word:

FRIEND – FIEND, FEAST – FAST, THERE – HERE, THOROUGH – ROUGH, FLIGHT – FIGHT, WONDERFUL – WOEFUL, RESIGN – REIGN, ENDURING – ENDING, PEST – PET, COVERT – OVERT

FEATURED

Repetitive

You have two groups of words:

  1. black, word, English, brief, noun, grandiloquent, last
  2. white, number, Russian, long, verb, unpretentious, first

To which group does “repetitive” belong?

The first group contains self-explanatory words (known as autologicals), the second group does not. Therefore “repetitive” should belong to the first group.