The word 整天 is formed by combining two characters: 整 (zhěng), meaning "whole" or "entire", and 天 (tiān), meaning "day". The construction is a straightforward semantic combination where the first character modifies the second, directly creating the literal meaning of "the whole day" or "all day long". It is a fixed, idiomatic compound where the individual meanings of the characters transparently contribute to the unified concept.