noun · measure word for relatives, marriages, or fields of study

这门子亲戚早就断了往来。

noun · a door, gate, or small opening

这院子后头有个小门子。

noun · a gatekeeper or a hanger-on of an aristocrat in former times

那门子见他穿得破烂，便不放他进去。

noun · social influence, connections, or informal channels to achieve an end

他想通过走门子找一份好工作。