I’m not a native English speaker and not a good math reader too. My question came while I reading this Debreu article about a existence of a real function to represent the preferences and I’m stuck in this passage:
If $A$, $B$ are two $f$-sets (resp. $i$-sets) and $A \cap B$ is not empty, then $A \cup B$ is an $f$-set (resp. $i$-set).
What’s this “resp.” means?