A chemical formula that indicates the simplest numerical ratio of the elements within a molecule, without demonstrating the molecule's chemical bonds or structure. For example, the empirical formula for water is H2O. Synonym: molecular formula.
Pelvic inflammatory disease (PID) is an infection caused by bacteria. When bacteria from the vagina or cervix travel to your womb, fallopian tubes, or ovaries they can cause an infection. Most of the time, PID is caused by bacteria from chlamydia and gonorrhea. These are sexually transmitted infections (STIs). Having unprotected sex with someone who has an STI can cause PID.
Many types of bacteria can cause PID. The bacteria found in 2 common sexually transmitted diseases (gonorrhea and chlamydia) are the most frequent causes. Normal bacteria found in the vagina and on the cervix can cause PID, but this is rare.