濃度
のうど · noudo · JLPT N2 · noun
concentration
濃 (thick, dense) + 度 (degree) = how thick a mixture is, i.e. its degree of density or concentration
濃 means thick or strong, as in tea or soup. 度 means degree or level. Together they measure how much solute or stuff is packed into a given volume.
度 — 广 (shelter) + 庶 abbreviated (phonetic)
Originally depicted a hand measuring length under a shelter, meaning 'to measure' or 'a measure/standard.' From this came extended senses like 'degree,' 'extent,' and 'to pass through' (as in passing time). The reading 'dù' means degree/measure, while 'duó' preserves the older verbal sense of measuring.