Confusing terminology in Fedora and Ubuntu

What is called 'orphan', and what is 'obsolete'? Fedora and Ubuntu give us contradictive and confusing definition.

Let's have a look here.

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Fedora:

"package-cleanup(1)"
--orphans
List installed packages which are not available from currenly configured repositories.
--leaves
List leaf nodes in the local RPM database. Leaf nodes are RPMs that are not relied upon by any other RPM.

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Ubuntu:

--'synaptic-status-installed(local or obsolete)'
Display only packages that are not (for longer) included in one of the specified repositories.

--"deborphan"
deborphan finds "orphaned" packages on your system. It determines which packages have no other packages depending on their installation and shows you a list of these packages.

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Accordingly, orphans(fedora)=obsolete(ubuntu), leaves(fedora)=orphan(ubuntu).