13 letters · 17 points in Scrabble
adjective (of words) interchangeable in a given context without changing the import of the expression
adjective capable of being exchanged for another or for something else that is equivalent
originEtymology tree English substitute Proto-Indo-European *-tḗr Proto-Indo-European *-dʰlom Proto-Indo-European *-dʰlis Proto-Italic *-ðlis Latin -bilis Latin -ābilis Old French -ablebor. Middle English -able English -able English substitutable From substitute + -able.
Etymology from Wiktionary, CC BY-SA 3.0