In the world of finance, there is a commonly used terminology known as the Elliott wave theory. This theory explains the three-wave countertrend price movement. The first wave, known as Wave A, goes against the market trend. Next comes Wave B, which is a corrective wave to Wave A. Lastly, Wave C completes the countertrend price move. Followers of this theory closely examine the A and C waves, using numbers from the Fibonacci series to identify potential price ratios. It is a widely studied concept in the field of finance and can provide valuable insights into market trends.