低下
ていか · teika · JLPT N2 · noun
decline
🍂 低下 = 低 (low) + 下 (down): both parts point downward, so it means fall or decline
低 means low and 下 means down or beneath. Together they describe something moving downward, used for falling levels, such as temperature, sales, or ability.
低 — person radical 亻 + 氐 (base)
A semantic-phonetic compound. The left side 亻 (person) gives the meaning, while 氐 supplies the sound and originally depicted something reaching the ground or base. Together they suggest a person bowing low, which extended to the general sense of 'low' in height, position, or degree.
下 — horizontal line 一 + mark below
下 is an indicative character: a long horizontal line represents a reference level, and a shorter stroke placed beneath it points to the area below. The original meaning 'below, down' comes directly from this spatial diagram, and it later extended to verbs like 'descend' and 'lower'.