The word "好久" is formed by directly combining two independent characters, each carrying its own core meaning, to create a new, unified concept. The first character, "好" (hǎo), here functions as an intensifier meaning "quite" or "very", while the second character, "久" (jiǔ), means "a long time". Their formation is a straightforward, conceptual fusion where the modifier "好" amplifies the inherent meaning of "久", resulting in the composite idea of "a very long duration" or "quite a while".