In philosophy, substance means, approximately, that element of an object without which it would not exist. In the millennia-old Aristotelian tradition[?], as well as early modern[?] traditions that follow it, substances are treated as having attributes[?] and modes[?].
... and the vaginal opening.
In the human male, the urethra is about 8 inches (200 mm) long and opens at the end of the penis.
Medical problems of the urethra:
...