一个朋友发短信问我，AM是什么意思？

我的第一反应是：上午 before noon

调幅 Amplitude Modulation

然后我问他，是不是还有FM啊？

这兄弟告诉我，与OEM相对的，汽车界的。

想了想，OEM是前装市场，Original Equipment Manufacture(原始设备制造商)

那AM应该是售后的吧，就告诉他是后装相关的，但不确定是什么的缩写。就让他确定下是不是after manufacturing。

晚上回来核实了一下，其实不是，是aftermarket。

另：原廠零件(OES, Original Equipment Service) 及非原廠廠零件(AM, After Market)

维基上的解释如下：
# Aftermarket (automotive), the addition of non-factory parts, accessories and upgrades to a motor vehicle.
# After-market (general), any market where customers who buy one product or service are likely to buy a related, follow-on product. For example, customers who install a software package will constitute an after-market for software support services.
# Aftermarket (finance) or Secondary market is the financial market for trading of securities that have already been issued.