Possible sources of this phenomenon are identified by intersections on a Campbell diagram. “Tongues” of this phenomenon may be found with the Mathieu equation when considering its “parametric” form. A “universal” curve for this phenomenon is quantified by the half bandwidth of a Lorentzian function. Injection (10[1])locking may cause the “sympathetic” form of this phenomenon. (10[2]-5[1])This phenomenon occurs more intensely but in a more narrow region when the Q-factor (10[1]-5[1])is high, (10[8]-5[2])corresponding (-5[5])to (10[1])underdamped (10[4])systems (10[4]-5[2])with (-5[1])little (10[3])energy (10[2]-5[2])loss. (10[5]-5[4])This (10[1])phenomenon (10[1])is typically distinguished (10[1])from the self-exciting (10[1])aeroelastic flutter that caused (10[1])the collapse (10[1])of the (10[2])Tacoma (10[1])Narrows (10[2])Bridge. (10[13]-5[2])For 10 (10[3])points, (10[10]-5[4])name (10[1])this (10[1])phenomenon (10[3]-5[2])in which an oscillator (10[2])driven (10[1])at (10[1])its natural (10[1])frequency (10[2])grows (10[3])in amplitude. (10[3])■END■ (10[23]0[14])