Is there a name for the operands of union and intersection?

Question

For subtraction, in $a - b$, we call $a$ the minuend and $b$ the subtrahend. With logical conjunction, $p \wedge q$, we can call $p$ and $q$ the conjuncts.

Are there terms like this for the operands of set union? Is there a term for $P$ and $Q$ in $P \cup Q$?

Likewise, are there terms for the operands of an intersection?

Answer 1

The word subtract comes from the Latin verb subtrahō, whose conjugation gives subtrahendus as the future passive participle ('which is to be removed'), and thereby subtrahend in English. The English word minuend is likewise derived from the future passive participle (minuendus, 'which is to be made smaller') of minuō. Similar derivations include:

• integrō > integrandus > integrand
• sūmō > sūmendus > summand
• multiplicō > multiplicandus > multiplicand

So following the same derivation:

• The word intersect coming from Latin verb intersecō, whose future passive participle is intersecendus, leading to intersecend (or more likely intersecand, to give a hard 'c').
• The word union comes from the Latin verb uniō, whose future passive participle is ūniendus, leading to uniend (or perhaps uniand).

That said, I have never seen the words intersecand or uniend, so using them will probably cause more confusion than it is worth.

...in fact, prior to reading your question, I had never heard the words minuend or subtrahend, either.

Answer 2

How about "disjuncts" for $p \vee q$. And then just "conjuncts" and "disjuncts" again for $P \cap Q$ and $P \cup Q$ respectively (since those set theoretic operations are defined by applications of "and" and "or"). Sounds good to me, at least, although I've never even heard of "conjuncts".