When the solid has a high affinity for water - in which case it is called hydrophilic (high energy e.g. glass)- water spreads. In the opposite case of hydrophobic (low energy e.g. teflon) surfaces, water does not spread but, instead, forms at equilibrium a spherical cap resting on the substrate with a 'contact angle'.
Infections such as trichomoniasis, gonorrhea, and Chlamydia (all STDs); and yeast infection can all cause vaginal discharge. Vaginal discharge can be associated with other symptoms such as burning or itching. Antibiotics are given for infections that cause vaginal discharge.
Chlamydia. Chlamydia is the most commonly reported STD in the U.S. It's spread mostly by vaginal or anal sex, but you can get it through oral sex, too. Sometimes you'll notice an odd discharge from your vagina or penis, or pain or burning when you pee. But only about 25% of women and 50% of men get symptoms.