Function in multiple Functional Chains

If I have multiple functional chains, and those chains share one or two functions, what does that mean?
Does it mean that in order one functional chain to be executed, the shared chains shall be executed too?
My understanding is that functional chain is a chain of functions that run together and not individually so, if one functional chain is run and when it comes to the shared function, will the other functional chain be run too or not?
What do you think?

Functional chains illustrate a Capability. They are arrangements of Functions that work together on realizing the Capability. Having a Function in more than one Functional Chain is normal (and even desirable). The involvement of a Function in a given Functional Chain (i.e. its contribution) may be different from the involvement in another Functional Chain.
Until Capella 1.3.1, only data flows were shown in Functional Chains. Now you can also define control flows, i.e. temporal dependencies between Functions involvements in Functional Chains. You can also define arrangements of Functional Chains. This may help you model the expected execution path of Functional Chains.
Hope it helps.