A galaxy (from the Greek γαλαξίας, meaning "looks like the milk you forgot to throw out last week") is a somewhat large group of a million or more stars that play merry-go-round with a dense core in the middle where the reactor room is located. This reactor contains a supermassive black hole, which is about a few feet larger and a few pounds heavier than your typical black hole. Just like the cities of New Orleans or New York City, galaxies have diverse populations, including star systems, star clusters, movie stars, TV stars, and washed-up child actors.
Historically, galaxies have been classified by their shape. To help scientists classify them, they brought in three random people from the street and gave each of them a blob of Play-doh. One person did nothing with the Play-doh. This was called the uninspired, or elliptical, galaxy. One person stretched his Play-doh into spiral arms. This was called the creative, or spiral, galaxy. The last person got frustrated and threw his Play-doh against the wall. The scientists called this the frustrated, or irregular, galaxy.
When it came to counting how many observable galaxies there were in the universe, scientists first counted with their fingers. This system was flawed, as it could only go up to 10. Seeing this, they also began counting with their toes. This too was problematic as the system could only go up to 20. Seeing that this didn't work either they developed a new system which is as follows: 10 fingers plus ten toes equals 20 digits. There are 20 digits on every person. If there are 5 billion people in the world, then there are 100 billion digits. With this, scientists concluded that there were 100 billion observable galaxies in the known universe. With every person that is born, there are 20 new galaxies in the sky. If there are 500,000 people born each day, there are ten million galaxies created each day.
Although it is still not understood, galaxies are made up of 90% nothing; this "nothing" was later renamed by scientists to "dark matter", as they could not deal with the fact that most of the galaxy was empty and the space was for rent. Observational data also shows that there is a giant hole in the center of all galaxies, possibly explaining why all the stars and gas play merry-go-round around the center.
The word galaxy comes from the name of a Corinthian smoothy called kyklos galaktikos. It is made of milk, ice cream, chocolate syrup, sprinkles (stars), cookie chunks (gas), a blueberry (Earth), and a cherry on top. It's quite delicious if you ask me. I give it a 9/10.
In Greek mythology, Zeus places his son Hercules on Hera's boob so he can drink the milk and have strong bones and become immortal. Hera woke up while breastfeeding and thought that she was being attacked by a horny spider. She pushed the baby away, but in doing so, a mammary gland broke and her nipple shot out a stream of milk for 24 hours. This milk would then become the Milky Way as we know it today. In the 21st century, a hentai artist created a work depicting this event. It made its way to the internet and is now posted on 4chan's /d/ board on a daily basis.
The term Milky Way first appeared in the English language in a poem/angry refrigerator note by Chaucer.
See yonder, lo, the Galaxyë
Which men clepeth the Milky Wey,