When you search an online encyclopedia, you are searching a compendium of information on just about everything. A compendium is a comprehensive collection of something.
You can also use the word compendium to describe a collection of written works. If you gather all of the anecdotes your parents and grandparents have told you into a book, you'll have created a compendium of family stories. The plural of compendium is either compendiums or compendia.
A cluster is a small group of people or things. When you and your friends huddle awkwardly around the snack table at a party, whispering and trying to muster enough nerve to hit the dance floor, you’ve formed a cluster.
Cluster comes to us from the Old English word clyster, meaning bunch. Nowadays, you can use cluster as either a noun or a verb. When we were kids, we would stand in a cluster (noun) on the street corner, eagerly awaiting the appearance of the Good Humor truck every afternoon. Then we would cluster (verb) eagerly around the driver, demanding ice cream. Virtually anything can form a cluster — flowers, cells, stars, human beings, and even events.
An estuary is the place in the water where a tide and a river current meet, like the estuary at New York Harbor, where the Hudson River meets the Atlantic Ocean.
Estuary, pronounced "ES-choo-air-ee," comes from the Latin word aestuarium, meaning "a tidal marsh or opening." The calm waters of an estuary, where the mouth of a river connects with the open sea and fresh water mixes with salty ocean water, makes the perfect home for many species of aquatic plants and animals. Chesapeake Bay and Puget Sound are estuaries.
Detention is a word for confinement or imprisonment, usually for a short time. It's also a punishment where children must stay after school.
If you're in detention, you probably did something wrong: you're being confined against your will. The police hold people in detention, and so do military forces. Usually, detention is a short period of confinement, like if someone is arrested and then released. Also, the word is commonly used for an after-school punishment for children who have to stay in detention instead of going home. One thing is true of both kinds of detention: no one wants to be there.
Migration is the movement of either people or animals from one area to another. Look up in the trees, where you might see a Monarch butterfly make a stop on its migration to Mexico.
Migration can be used for the journey from one place to another or for the act of movement. Thousands of mid-western farmers made the migration to California during the dust bowl. Demographers have noted the migration of young people to the big cities presumably for work. With animals, it’s almost always in reference to a seasonal change in location. On boat tours, you can see the whales during their annual migration down the West coast.