Prophecy

A prophecy is a claim of what the future will be like, which is not based on any ordinary source of information. Prophecies are found in most religions. Not all people believe in prophecy. People that do think they come from God or a god. They are often hard to understand and need interpretation. Very often, they concern one very specific event. People who make prophecies are called prophets. In Ancient Greece, people who made prophecies were called oracles, most notably the Oracle of Delphi. Since then, people like Nostradamus have made prophecies.

To prophesy is to make a prophecy. The two words are spelled differently and pronounced differently. "Prophesy" is a verb, and "prophecy" is a noun.

Prophecy in religion

Judeo-Christian Religion 
There are many prophecies in the Bible. Some of these warn of punishments to come.  There are two kinds of Bible prophecies.  Some are conditional, that is, they include the possibility that the punishment can be avoided based on the hearers changing their ways.  An example of this is found in the Book of Jonah.  Other prophecies are unconditional.  That means that the event will happen no matter what the hearers do to avoid it. There are also Bible prophecies that tell of future blessings.  Blessings are good things that happen because of God's mercy and forgiveness. Some prophecies contain both punishment and blessings.  Jesus made prophecies like this, warning people to believe in Him and live right, to get the blessing instead of the punishment. While some of the prophecies in the bible about future events are hard to understand, the moral warnings from Jesus are not hard to understand.  For this reason, some preachers, like Moses, Jesus and other religious leaders who tell people to live a good life are called prophets by their followers even though they may not tell about future events.

False Prophecies
Sometimes people think that God has told them something or that they have discovered something in the Bible that tells the future.  Predictions of the end of the world have been made many times in history. 
When people set dates for events such as Christ's return, they have often been disappointed. . Jesus himself said that "No one knows the day or the hour" of his return.

Prophecies not related to religion 

Scientists sometimes make predictions about the future. These may be correct but often are wrong or only partly correct.  The famous inventor Thomas Edison predicted that electricity would replace steam as a way to power trains, but he also predicted that gold could be made from iron, making it worth little as money.  Einstein said in 1932 that atomic energy would never be possible.  Politicians also make prophecies that may or may not prove to be true. Adolph Hitler predicted that the Nazis would rule for 1000 years, but they were defeated in only 12 years(1933-1944).  Many organizations try to predict the outcome of elections, with very mixed accuracy.  Others predict the winners of sporting events, but are often wrong. Games with unexpected results are called "upsets". A famous baseball player, Yogi Berra once said that "It's tough to make predictions, especially about the future".

Self-fulfilling prophecies 

Sometimes people act in ways that have been previously prophesied. If they do this intentionally, this is called a "self fulfilling prophecy". Abraham Lincoln said "The most reliable way to predict the future is to create it." A negative way this works is when someone thinks they will fail at something, as so they don't try very hard to achieve it.  

Theology
Future