From time to time I ask you to indulge my curiosity about a matter of language, especially when I’m stumped.
Recently, you helped me with “one of the more” versus “one of the most,” though no one cited an authoritative source as I had hoped. It seems many of us know how an idea should be expressed in words, but we don’t always know why. I like to know why.
Here’s another one that has had me stumped for years, decades actually; I just never bothered to drill into it.
It was nearly 20 years ago that I began to wonder what the difference was between nouns ending in “ence” and those ending in “ency.”
A leadership phrase swept the corporate world decades ago: “core competency.” All through the ’80s and ’90s, the company for which I worked kept tens of thousands of employees busy perfecting and touting our core competencies. I wondered then what the difference was between competency and competence.
Lately, I’ve wondered about the other “ence” nouns: resilience, dependence, independence, even interdependence. They all have “ency” alternatives.
The question of the day is: Are there specific instances in which “ence” is correct but “ency” is not and vice versa?
Generally speaking, the answer isn’t easy to find, not for me, anyway. When you consult a dictionary, the answer is no.
My first sweep through a dictionary revealed that, in most cases, one is an alternate use, or more or less common use, of the other. In other words, they mean the same thing.
I wasn’t going to take that at face value. There had to be nuances beneath.
Not surprisingly, there are esoteric distinctions. For example, dependence is a term specific to the fields of mathematics and science.
As I often do when I go a-hunting for the truth and don’t find it in the dictionaries or stylebooks, I poke my head into an online chat. After a long night of peeking and poking, I came closer to gleaning the differences.
The “ence” noun pertains to a state of being: of being competent, dependent, independent, resilient. The “ency” form suggests a degree of that state, based on specific attributes.
For example, competence is the ability to perform a task, while competency is the knowledge, skills and abilities that distinguish superior performer from an average one.
Resilience is the ability of something to return to its original condition after being stretched or compressed, while resiliency is the physical (or mental) property that enables something or someone to return to its original condition.
Am I drawing an accurate conclusion or just searching for absolute truth where none exists?
Once again, your opinion is welcome, and your sources even more so.
Perhaps I just need a crash course in mining.
Word Nymph 
Well, first:
Reading any kind of management literature will quickly turn your brain to mush. These are people really straining to justify their existence and their huge consulting fees. Part of making something sound “new” is to make up new words where old words would do just fine, or use obscure words for very simple ideas. “Competency” is less used than “competence”, so somebody thought is would sound newer, or more specialized, to somebody.
There is no difference between “competence” and “competency”. The only such pair of words I know of in which there’s a clear difference of meaning is “dependency” in international law. Puerto Rico is a dependency of the U.S. “Dependence” is the relationship it has to the U.S.