(uncountable) The state or quality of being sound. / (countable) The result or product of being sound. / (logic) The property (of an argument) of not only being valid, but also of having true premises.

plural of soundness

A sensation perceived by the ear caused by the vibration of air or some other medium. / A vibration capable of causing such sensations.

(intransitive) To produce a sound. / (copulative) To convey an impression by one's sound. / (intransitive) To be conveyed in sound; to be spread or published; to convey intelligence by sound.

(Britain, Ireland, slang) Yes; used to show agreement or understanding, generally without much enthusiasm.

A long, thin probe for sounding or dilating body cavities or canals such as the urethra; a sonde.

(intransitive) Dive downwards, used of a whale. / To ascertain, or try to ascertain, the thoughts, motives, and purposes of (a person); to examine; to try; to test; to probe.

Soundly.

Healthy. / Complete, solid, or secure. / (mathematics, logic) Having the property of soundness. / (Britain, Ireland, slang) Good; acceptable; decent. / (of sleep) Quiet and deep.

(geography) A long narrow inlet, or a strait between the mainland and an island; also, a strait connecting two seas, or connecting a sea or lake with the ocean. / The air bladder of a fish.