strength vs toughness

strength and toughness both are nouns.

Word	Noun	Adjective	Verb	Adverb
strength	Yes	No	No	No
toughness	Yes	No	No	No

As nouns, toughness is a hyponym of strength; that is, toughness is a word with a more specific, narrower meaning than strength:

strength (noun)	toughness (noun)
the property of being physically or mentally strong	the property of being big and strong
an asset of special worth or utility	enduring strength and energy
permanence by virtue of the power to resist stress or force	impressive difficulty
the amount of energy transmitted (as by acoustic or electromagnetic radiation)	the elasticity and hardness of a metal object; its ability to absorb considerable energy before cracking
capability in terms of personnel and materiel that affect the capacity to fight a war
physical energy or intensity
capacity to produce strong physiological or chemical effects
the power to induce the taking of a course of action or the embracing of a point of view by means of argument or entreaty
the condition of financial success