soften

To make soft or softer.

To undermine or reduce the strength, morale, or resistance of.

To make less harsh, strident, or critical.

To become soft or softer.

To remove from (natural water) the hardness due to the presence of salts of calcium or magnesium in solution. In the case of temporary hardness, boiling the water or adding to it a carefully determined proportion of calcium hydroxid is used to produce softening; in the case of permanent hardness, sodium carbonate, not in too large excess, may be added. See hardness, 2.