机关
jīguān · HSK 6
mechanism
⚙️ 机 machine + 关 gate = hidden gears behind the door
A mechanism is the machinery behind a closed gate — concealed parts that make things work. By extension, a stratagem: the secret moves operating behind the scenes.
关 — door 门 + simplified 关 inside
关 is the simplified form of 關. The traditional character showed a gate (門) with a bolt or crossbar inside, depicting a barred door — hence 'to close' or 'shut'. Meaning later extended to 'pass' (a guarded gate), 'barrier', and figuratively 'concern' or 'connection'.