How to distinguish male and female cores of photovoltaic panels

To identify a solar panel's polarity, check the MC4 connectors (male/female) or use a multimeter (DC voltage mode)—positive terminals show +V (e., +18V for a 20W panel), negative reads -V or zero. . So is male/female reckoned by the outside appearance or inside structure? And, does the male connect to the + or - side of the panel? This site illustrates the plastic housing which looks like a male body part and calls it female. html This site says. . What is the difference between male and female socke every solar connection lies the simple concept of male and female connectors. This is actually opposite to conventional thought. When connected,the pin and socket form a tight electrical connection. [pdf]