I saw several times that often some data describing certain
algebraic objects,
eg the set of cells of a simplical complex
or a Cech cycle of a chosen coving of a variety
are called *"combinatorial data"* or "encoding combinatorial data".

My question is simply what is the justification of the name "combinatorial" here? what is combinatorial on these data?

More generally can it be precised when a certain data describing an algebraical object is called "combinatorial"?

A short UPDATE to precise what I mean (literally that's the comments below):

The meaning of "combinatorial" for *abstract simplicial complexes* is pretty easy to see: indeed, a data consisting of set of vertices $V=\{ v_1,v_2,...,v_n \}$ and a $m$-simplex of $S$ is defined as a subset $\{ v_{i_1},...,v_{i_m} \}$ of $V$. then a subset $S$ of power set $P(V)$ of $V$ is called abstract simplicial complex if for every $m$-simplex $\{ v_{i_1},...,v_{i_m}\}$ contained in $S$ every subset $\{ v_{i_{j_1}},...,v_{i_{j_d}} \}$ is (as a $d$-simplex) is contained in $S$ as well.

Therefore obviously not every subset of the power set $P(V)$ of $V$ is a abstract simplicial complex. So to determine which subsets of $P(V)$ can occure as abstract simplicial complexes is a combinatorial problem. That's where I see the "combinatorial flavour" here. So I think that this is precisely the justification for the word "combinatorial" if one can associate to an algebraic or topological object an abstract simplical complex encoding sometimes a lot of information about the original object. (the most prominent example is surely the Nerve theorem which desides when this "combinatorial data" essentially suffice to reconstruct the original object up to homotopy).

But how to draw the same analogy to Cech cycles isn't clear to me. Is it possible to associate abstractly a abstract simplicial complex to a Cech cycle in order to "make" it combinatorial?

combinesimplices to form a simplicial complex. $\endgroup$ – Carlo Beenakker Jul 11 '20 at 21:38