Terms “cut off” and “tail off” about ACF, PACF functions

I’m trying to understand the meaning of cut off and tails off in time series plot of ACF and PACF.enter image description here

What “Cut off after lag” mean? This about limit?

What “Tails off” mean?

In the example above, the book that I’m using to study, say that is an AR process.

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But I can’t figure out the meanings of “cuts off” and “tails off”

Answer

“Cuts off” means that it becomes zero abruptly, and “tails off” means that it decays to zero asymptotically (usually exponentially).

In your picture, the PACF “cuts off” after the 2nd lag, while the ACF “tails off” to zero. You probably have something like an AR(2).

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Source : Link , Question Author : Community , Answer Author : Chris Haug

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