高效
gāo xiào · HSK 7
efficient
⚡ 高 = high + 效 = effect; high-effect = efficient
高 means high or tall; 效 means effect or result. Together: high-effect, i.e. producing strong results — efficient. The 效 character contains 攵 (the 'action' radical), tying it to doing/producing.
高 — pictograph of a tall building/tower
高 is a pictograph of a tall structure, likely a watchtower or multi-story gate, with a roof on top, an upper chamber, and a base below. From this concrete image of height it extended to the general meanings 'tall,' 'high,' and figuratively 'lofty' or 'noble.'