different between faithlessness vs faithless

English

faithless +? -ness

faithlessness (countable and uncountable, plural faithlessnesses)

From Middle English feithles, equivalent to faith +? -less.

faithless (comparative more faithless, superlative most faithless)

Lacking faith; lacking belief in something.
Not believing in God, religion, or a comparable ideology.
Unfaithful (said of people, towards their partners)
- 1996, Frederick Ahl, Hanna Roisman, The Odyssey re-formed, p. 283:
  Menelaus, who fought to recover his faithless wife, has clearly rooted himself in Sparta for the remainder of his life […]
Not observant of promises or covenants.
Not true to allegiance, duty, or vows
Synonyms: perfidious, treacherous, disloyal
Serving to disappoint or deceive
Synonyms: delusive, unsatisfying

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