54769
The frequency of a wave is its rate of oscillation and is measured in hertz , the SI unit of frequency , where one hertz is equal to one oscillation per second .
 second
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 second