The Gearbox Enigma

What is the function of a gearbox?
What is the function of joints?
What is the name for a distribution that is bell-shaped and symmetrical?
What is the name for a quadrilateral with four sides of equal length?
What is the name for a test of significance that compares the means of more than two groups?
"Which word is similar to sepulcher?
Which word is similar to platonic?