Codex is my personal math journal.
Structure
Codex is organized by branches and topics. Each page discusses a specific concept. For example, Inverse Function is a concept from the topic Functions, which belongs to the branch Set Theory.
Every page, i.e. every concept, has a unique code name. For example, the code name of Generated Subgroup is GEN.
Codex mostly consists of entries, which look like this:
…
Each entry could either be an axiom, a definition, a proposition or a remark. Here, proposition is a generalized term for mathematical results, including theorems, lemmas, etc.
Other Notes
We work in $\ZF$ or $\ZFC$ by default.