Thank you for your good wishes! I’m fine and doing quite well.
I would define “stock knowledge” as the set of structured, systemic, and contextual information that one has already learned and internalized; it is preexisting knowledge, as opposed to knowledge that one doesn’t have or has yet to learn and understand.
As to “stack knowledge,” I must tell you that whatever it means isn’t part of my stock knowledge yet. This is my very first encounter with that noun phrase, so I can’t tell you offhand how it might differ from “stock knowledge.” In fact, a cursory search on the web has convinced me that “stack knowledge” doesn’t exist in the English lexicon at all.
You see, there are strings of words in English that are known as collocations—familiar groupings of words that commonly go together and convey meaning by association. To this category of words belong such verb phrases as “feel free,” “make progress,” and “save time”; such noun phrases as “powerful computer” and “strong coffee” (as opposed to “strong computer” and “powerful coffee,” respectively, which are very poor collocations); and such idiomatic expressions as “gone with the wind,” “straight as the crow flies,” and “tempest in a teapot.”
The noun phrase “stock knowledge” is clearly a strong collocation that consists of the noun “knowledge” modified by the adjective “stock” in the sense of “commonly used or often brought forward.” On the other hand, when looked upon as a noun phrase, “stack knowledge” doesn’t qualify as a collocation because it fails to convey a clear and identifiable meaning by association. Differentiating “stock knowledge” from “stack knowledge” is therefore like differentiating apples from desktop computers, which is clearly not a very meaningful exercise.
Indeed, “stack knowledge” won’t sound nonsensical only when we look at “stack” as a verb in the sense of “to arrange in an orderly pile or heap,” with “knowledge” as its direct object. We can then use “stack knowledge” in a sentence like, say, “The function of a computer’s hard disk is to stack knowledge in a memory bank for long-term storage.” This is a very unnatural-sounding sentence, of course, but we can make it semantically more precise by replacing the word “knowledge” with “information.” This time, the verb phrase “stack information” works very well because it’s a fairly strong collocation by itself.
