Splitting of primes terminology doubt

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What do we mean when we say that a given prime $p$ splits completely in an algebraic extension of $\mathbb Q$?

Are we talking about the splitting of prime ideals into unique factors? And, in that case, we do we mean by "complete" splitting?

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In an algebraic extension $F:\mathbb Q$, the ideal $p\mathfrak o_F$ can be written as a product of prime ideals. If the product has $[F:\mathbb Q]$ factors, $p$ splits completely; if the product has only one factor, $p$ is inert. Anything inbetween may happen (not to mention ramification, i.e., the occurance of repeated factors). Maybe you have so far considered only quadratic extensions, where there isn't really anything "inbetween" possible?