You're in the wrong place. Or, to be precise, you've used the wrong words. What you're looking for is over here:
In the event that the obvious somehow eluded you, this page is a redirect. It's a digital signpost, a ghost in the machine that exists for the sole purpose of correcting a common, if tiresome, imprecision in terminology. It points from 'Casimir operator' to 'Casimir element' because, while related, they are not the same, and one of them is the subject of an actual article.
And because humanity possesses an inexhaustible need to categorize its own breadcrumb trails, this particular redirect is tracked and monitored with a level of scrutiny that borders on the obsessive. The following categories are employed to keep this digital void neatly filed:
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From a related word or phrase: This is the designation for when a redirect connects a word or phrase (or term, if you insist on being formal) to a page title that is conceptually adjacent but not identical. Think of it as a sibling, not a twin. In this context, 'operator' and 'element' are closely related within the language of Lie algebra, but the distinction matters. This redirect exists because someone searching for the 'operator' is almost certainly looking for the 'element', and it's easier to point them in the right direction than to let them wander off into the weeds. It’s a useful search term, a common misstep, and perhaps even a candidate for a Wiktionary link, should someone ever feel the need to immortalize the distinction in a dictionary.
Do try to keep up, because this is where the pedantry becomes truly exquisite. A redirect from a related word is not, I repeat, not the same as one correcting a simple typo, which falls under redirects from alternative spellings. This is about nuance, a concept I'm sure you're familiar with. It is also fundamentally different from redirects that serve as subtopics or point to related topics. The critical difference—the one that keeps the wiki-architects awake at night—is that a 'related word or phrase' like this one is deemed unlikely to ever warrant its own, sprawling article. It doesn't merit a dedicated section in the target page, nor does it possess the latent potential to one day blossom into an independent article, template, or project page. It is, and will likely remain, a conceptual echo, forever tethered to the primary entry.
Finally, in the grand, automated tapestry of this place, should this page ever attract the wrong kind of attention, its protection levels are automatically sensed, described, and categorized. A silent, algorithmic guardian watching over a signpost in the digital wilderness. A truly thrilling thought.