48821
Naturally occurring , with a half-life of 1.25 years , decays to stable ( 11.2 % ) by electron capture or positron emission , and also to stable ( 88.8 % ) by beta decay .
 half-life
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:
 half-life