- inf (infimum) is the greatest-lower-bound data point.
- sup (supremum) is the lowest-upper-bound data point.
- lim inf is the greatest-lower-bound Y data point when X approaches some certain value (needn't be infinite) specified under lim inf's limit subscription. (note that both inf and sup cannot have limit subscription)
- lim sup is the lowest-upper-bound Y data point when X approaches some certain value (needn't be infinite) specified under lim sup's limit subscription.
All these four terms are used for data sequences that may look either flutuate (like converging waves) or smooth curves (so inf = sup and lim inf = lim sup).
https://math.stackexchange.com/questions/422964/what-is-limit-superior-and-limit-inferior
https://en.m.wikipedia.org/wiki/Limit_inferior_and_limit_superior
https://en.wikipedia.org/wiki/Infimum_and_supremum
https://math.stackexchange.com/questions/1031905/lim-inf-and-lim-sup-convergence-divergence
