Nuisance Suffixes

An overseas client messaged me with the following question: "How do you choose between the suffixes <-ence> and <-ance>? For example, the word 'nuisance.' Could you help clarify this?

Yes, I can, and I will. But first, I'd like to point out that the spelling of allomorphic suffixes like <-ance/-ence>, <-ant/-ent>, <-able/-ible>, <-er/-or>, and others is something that even proficient adult spellers can be uncertain about, so it's ill-advised to try to hold children, especially struggling children, to some kind of high performance standard when it comes to these suffix pairs. As I always stress, it's more important to generate an accurate understanding of patterns than to focus on a correct performance.

These suffix pairs are frequently misrepresented in the so-called 'Science' of Reading arena. I've taught and written about these errors for years. I do get asked about these commonly misunderstood suffixes from time to time, so I figured I'd park an understanding here.