Most of these are not in common usage and would be unfamiliar to many native speakers. The first one I've never come accross Philtrum l know but it wouldn't occur to me to use in conversation. Cupids bow is reasonably common place but usually in relation to makeup, lipstick etc The sclera I've heard of but is usually used in a medical context, most people would say the whites of the eye The space between my eyebrows is just that, unless I'm talking about the frown lines usually found there 😁

These are not common words. None of them are in the most-common 10,000 words. Some dictionaries such as the Collins Dictionary give the frequency of a word. Collins groups words into the most-common 1,000 words, 4,000 words, 10,000 words, 30,000 words, and "rare." For example: sclera is in the most-common 30,000 words. https://www.collinsdictionary.com/dictionary/english/sclera In the future, you can check if a word is common by using Collins or a similar dictionary.

I've only ever heard of sclera. I would say it would be known by a fair number of people. I wouldn't say any of them would qualify as being in common usage.

I love you guys! Thank you for answering. It was really helpful!

The only one I have heard used is Cupid's bow. :)