Figuring out what I want to prioritize in making something can require defining terms. This is something to help me with what I'm working on right now. Another project might require not only different definitions but different language altogether. This is more about showing a part of a process than making a declaration of overall ethos or policy.
Threat- To include all enemies, hazards, and conditions such as worsening injury and worsening disease.
Enemies- To include animals, civilized humanoids, and monsters.
Hazards- To include traps, heat and weather, radiation, falls from heights, spreading fire or flood, etc.
Conditions- Highly situational impact, and nearly impossible to form a comprehensive list; ordered into broad categories whose severity varies according to the situation (must be kept somewhat fuzzy necessarily)
Civilized- To include creatures with a spoken, written, empathic, visual, psychic, pictographic, or other common language, even if it's an insular language and communication with other civilized creatures is impossible.
Humanoids- To include all shapes and variations on the same basic skeletal structure as Oprah Winfrey; or, a creature for whom no guesswork is required as to how it would wear blue jeans.
Animals- To include any normal fauna we would classify as such in the real world, including great apes and anything else that could otherwise fit into an above category (unless specifically ruled).
Monster- Any creature (living or dead, material or immaterial) which does not fit neatly into an above category, which can include strange but mundane fauna, those whose composition is influenced by alien or magical factors, and creatures who don't fit fully under the heading of "civilized humanoid."
Traps- Either deliberately created or deliberately exploited (existing cairn on a hill that is levered onto passersby below).
Mechanic- Agreement on a process
Ruling- Decision on a situation
Rule- Agreement on a decision
Economy- The measure of the exchange of a resource, such as number of choices or degree of success, or currency and favor in-fiction.
Bargain- A declaration of an economic action with the intent to obtain a profit.
Resolution- The interaction of a mechanic, rule, or ruling on an bargain.
Advancement- A reward tied to action outcome and time, i.e. a measure of experience.
Magic- Alternative causality, or literally rules exceptions.