fourier analysis – dominant frequencies extraction

I want to extract the dominant frequencies
And then based on the large amplitudes and their frequency, I will determine whether the new sample has a difference or not
So I did this:

1- I got the Fourier transform from the signal –>A

2- I wrote down the parts that had a large amplitude with their frequency.
–>amp(A) , freq(A)

Well, now I have the desired information (an array containing frequencies and an array containing amplitude ), but the challenge I face is that each of the content of amplitude and frequency must be indicated by one parameter at most.(1 parameter for amplitude and 1 parameter for frequency)

What comes to my mind is, for example, using the dot product of the array containing the frequency and the array containing the amplitude ( amp (A) . freq (A) ), but it does not seem appropriate, or for example, the average amplitude mean(amplitude) or standard deviation .etc, but nothing comes to my mind for the frequency.

It seems to me that we have a graph in two-dimensional space where the x-axis is the frequency and the y-axis is the amplitude
How can this graph be described and distinguished from other graphs with only 2 parameters?