One broad catagorization of numerical data is as continuous or descrete . Continuous data like height can take on any value over an interval or group of intervals. Data that can only assume certain values with no intermediate values or things that are essentially a counting function are discrete. More specific catagorization of quantitative data is as ratio , interval or ordinal . Ratio data have a natural ordering, differences are constant and there is a meaningful and natural 0 value.
Height is ratio data.
Notice it doesn't matter which units we use to measure. A height of 0 is the same in either inches or metric measurement. Interval measurement has a natural ordering, and differences are constant, but there is numrical values can not be directly compared. The numerical temperature and the value of 0 depends on which temperature scale you use. Ordinal data has only a natural ordering to it, i.e. first, second, third etc.