 As is also usual in the study of such spaces, it is usual to abuse notation and speak of a "function" in "L""p"("T"; "X") rather than an equivalence class (which would be more technically correct).Very often, the space "T" is an interval of time over which we wish to solve some partial differential equation, and "μ" will be one-dimensional Lebesgue measure.The idea is to regard a function of time and space as a collection of functions of space, this collection being parametrized by time.