1The action of sustaining or maintaining something. Also: the result of this; maintenance, preservation, upkeep. Compare "sustentation" Now rare.
2The sustaining or prolongation of a sound, especially a speech sound or a musical note.
3The quality of being sustained in argument or style.
Early 16th century; earliest use found in Lincoln Wills. Either from classical Latin sustent-, past participial stem of sustinēre sustain + -ion, after e.g. retention, etc., or an alteration of sustentation by association with the same models.