An Etymological Dictionary of Astronomy and Astrophysics

1. The state of a → mechanical system in which the → amplitude of → oscillation is increased when it is subjected to stimulus from another source at or near its own natural → frequency.
   

2. The condition of an electrical circuit with respect to a given frequency in which the net reactance is zero and the current flow a maximum.
   

3. A relationship in which the → orbital period of one body is related to that of another by a simple integer fraction, such as 1/2, 2/3, 3/5. → Laplace resonance, → Lindblad resonance, → resonance orbit .
   

4. → resonance particle.

Etymology (EN): Resonance, from M.Fr. resonance, from L. resonantia “echo,” from resonare “to resound,” from re- “again, back” + sonare “to sound.”

Etymology (PE): Bâzâvâyi, from bâz- “again, back,” → re-, + âvâ “voice, sound” (related to âvâz “voice, sound, song,” bâng “voice, sound, clamour” (Mid.Pers. vâng), vâžé “word;” Av. vacah- “word,” vaocanghê “to decalre” (by means of speech), from vac- “to speak, say;” cf. Skt. vakti “speaks, says,” vacas- “word;” Gk. epos “word;” L. vox “voice;” PIE base *wek- “to speak”) + -yi noun suffix.