效

Phono-semantic compound:

攴 (칠 복, “to strike, action”) — semantic component, denotes an action or effort.

交 (사귈 교, “to meet, to join”) — phonetic component, gives the sound 효 and suggests interaction.

Thus originally “to act in the manner of,” later extended to “to emulate, to produce effect.”

效果 (효과) — effect, result

效法 (효법) — to emulate, follow as a model

效忠 (효충) — to show loyalty

無效 (무효) — invalid, ineffective

效能 (효능) — efficacy, effectiveness

In Classical Chinese, 效 carried a stronger sense of “emulate or model oneself after,” while in Modern Chinese it primarily refers to “effect, efficacy.”