Word for "stepping stone" or "lemma"

Question

I seem to remember reading a definition for a word that conveyed the idea of "an instance of doing something that prepares one for something else". Something like a lemma but not restricted to mathematics.

Did that describe a word you know? I'm 95% sure there's actually a simple noun that specifically denotes something that you use to get ready for the more challenging version of the same thing.

My question isn't limited to what I'm writing right now, I'm just curious - but here is a little more context: I'm introducing the reader to game theory. I take her through two games. One prepares her for the other. It isn't practice, it's just getting familiar with it. I'd liken it to the climb to Everest base camp. In fact, you could use that, "The climb to Everest base camp is a ___ for the climb to the summit."

Answer 1

Preparatory step seems to fit your meaning.

Also intermediary step.

Also vehicle: you can call this intermediary step a vehicle toward further advancement.

But, why would you not use stepping stone? It's a perfectly acceptable phrase for that sort of thing.

Update

In response to the context given in comments:

Preliminary excerise is another good fit.

Also, Formative.

Not quite a fit, but a really cool word. Progymnasmata, Greek meaning fore-exercises refers to a series of rhetorical exercises to prepare students for future writing tasks.

Answer 2

Prerequisite: something required beforehand.

Precondition: something that must come before or is necessary to a subsequent result.

If a step is required before another step can be taken or prepares for that next step, then the required or preparatory step is a precondition or prerequisite.

Answer 3

A prelude perhaps. I think it's well understood outside its musical context.

Answer 4

It seems to me there's two slightly different things here. One is a necessary thing that you need before going on to the next stage, as in stepping stone - some good sugestions in the other answers.

The other is more about familiarising yourself with the situation before trying it for real:

dress rehearsal / trial run / dry run