For example, of the two words lion and lioness, lion is unmarked for gender (it can denote either a male or female) whereas lioness is marked, since it denotes only females. b. Explicitly characterized by or having a particular linguistic feature.
20 Hertz to 20,000 Hertz is the frequency response range that a human can hear. So in answer to your question 20 Hertz would be the lowest pitch a human can hear.
Frequencies lower than 20 Hz are beyond our frequency hearing range: our low frequency response test - which starts as low as 10 Hz - should remain inaudible until it reaches 20 Hz. If you hear frequencies below 20 Hz, suspect this test to be corrupted by Harmonic Distortion generated from your speaker or subwoofer.