son

The root son comes from Latin sonus (a sound, a noise) and its verb sonāre (to make a sound, to ring). It is one of the most literal roots in English: almost every son word is, in some way, about something making a noise.

Start with the bare root. sonus + the adjective ending -ic gives sonic — "having to do with sound." Because sound travels at a fixed speed, sonic came to mark that speed itself: a sonic boom is the crack you hear when an aircraft hits the speed of sound. From there the prefixes do the rest of the work:

- super- (above, beyond) + sonic → supersonic: faster than the speed of sound.
- ultra- (beyond) + sonic → ultrasonic: sound beyond the range human ears can hear — the pitch a bat or a medical scanner uses.

Now add the verb sonāre ("to ring"):

- re- (back, again) + sonāre → resonate / resonance: a sound that rings back. Strike a tuning fork near a piano and the matching string starts to ring on its own — that ringing-back is resonance. The image was so vivid that English borrowed it for emotion: an idea that resonates with you keeps ringing inside long after you hear it.
- con- (together) + sonāre → consonant / consonance: literally "sounding together." In music, notes that sound pleasant together are in consonance. In phonetics, a consonant is a speech sound that can only be pronounced together with a vowel — k, t, p cannot stand alone, they need a vowel beside them to be heard.
- dis- (apart) + sonāre → dissonant / dissonance: sounding apart, clashing. Musically it is the harsh, unresolved chord; figuratively, cognitive dissonance is the discomfort of two beliefs that clash inside your head.
- uni- (one) + sonus → unison: "one sound." When a whole choir sings the exact same note, many voices become a single sound — they sing in unison. The word then drifted from music to mean any perfect agreement: the team moved in unison.

A few family members keep the plain Latin meaning of "loud, full sound": sonorous describes a deep, rich, ringing voice, and sonar is a 20th-century coinage (SOund Navigation And Ranging) that uses sound pulses to map the seafloor. Two musical words came through Italian: sonata (a piece sounded on instruments, as opposed to a cantata, which is sung) and sonnet (literally "a little sound," a little song that grew into the fourteen-line poem).

The whole family follows one rule: keep your ear on the prefix. re- rings it back, con- rings it together, dis- rings it apart, uni- rings it as one, super-/ultra- push it past a limit. The root son never stops meaning "sound" — the prefix only tells you what the sound is doing.