How does Hendrich define the terms mayfly and albatross in the novel, How to Stop Time?

Mayfly and albatross are the terms that Hendrich and others use to describe normal humans and those with Tom's condition. The word mayfly is symbolic for the short number of years in a normal human life. The albatross was once believed to live a very long life, which is why Hendrich named his organization the Albatross Society. Tom is an albatross.