Speculation (noun)

1. Forming a theory or conjecture without firm evidence.
2. The act of buying or investing in something with the hope of making a profit but with the risk of losing money.
3. Consideration or discussion of a subject without definite knowledge or facts.

Origin:

The word "speculation" comes from the latin word "speculatio" which means "observing" or "consideration" and it first recorded use in the english language in the early 16th century.

Examples:

1. The news article was filled with speculation about the possible causes of the accident.
2. Speculation in the stock market can be risky.
3. His theory is based on speculation rather than solid evidence.
4. She was engaging in idle speculation about what could have happened.
5. Speculation about their future plans was the main topic of conversation among their friends.