A hypothesis is a possible explanation for something that is observed. For example, it is a common observation that objects that are thrown into the air fall toward the earth. Sir Isaac Newton put forth a hypothesis to explain this observation, which might be stated as 'objects with mass attract each other through a gravitational field. [1] (e.g. "If [I do this], then [this] will happen.")

References

A Strong Hypothesis, sciencebuddies.org