The Problem of Aliquis

New students are often fussy when words defy normal expectations. Take aliquis for an example. In Classical Latin, the word aliquis, aliqua, aliquid becomes quis, qua, quid after si, nisi, num, and ne. In fact, there's even another little rhyme to help remember:

After si, nisi, num and ne
All the ali's fall away.

So in Catullus' 76th carmen:

Si qua recordanti benefacta priora uoluptas,
est homini, cum se cogitat esse pium...

If there is any delight for a man recalling older
kindness, when he thinks that he has been dutiful...

Unlike quis the pronoun, the feminine singular nominative is aliqua, as is the neuter plural. However, aliquae is sometimes seen. Also, in neuter plural, you see both aliquid and aliquod.