Each coloured bar represents a section and is colour-coded for Earth sections (green) and Space sections (purple).

The grey bars represent the chapters, which are marked with ticks and numbers.

The y-axis is the relative frequency, i.e. the proportion of tokens in that section (or chapter) that are tagged as NOUN (so a bar might be higher, even with fewer occurrences, if the section or chapter is shorter).

Part-of-speech tagging was done with spaCy. The tagging uses Universal POS tags.