Hypothesis:

This is a tentative answer to the question: a testable explanation for what was observed. The scientist tries to explain what caused what was observed.
Hypothesis: Rotten meat does not turn into flies. Only flies can make more flies.
Hypothesis: There is no such life force in air, and a container of sterilized broth will remain sterile, even if exposed to the air, as long as bacteria cannot enter the flask.
In a cause and effect relationship, what you observe is the effect, and hypotheses are possible causes. A generalization based on inductive reasoning is not a hypothesis. An hypothesis is not an observation, rather, a tentative explanation for the observation. For example, I might observe the effect that my throat is sore. Then I might form hypotheses as to the cause of that sore throat, including a bacterial infection, a viral infection, or screaming too much at a ball game.
Hypotheses reflect past experience with similar questions (“educated propositions” about cause) and the work of others. Hypotheses are based on previous knowledge, facts, and general principles. Your answer to the question of what caused the observed effect will be based on your previous knowledge of what causes similar effects in similar situations. For example, I know that colds are contagious, I don’t know anyone with a cold, I was at the ball game yesterday, and I was doing a lot of yelling while I was there, so I think that caused my sore throat.
Multiple hypotheses should be proposed whenever possible. One should think of alternative causes that could explain the observation (the correct one may not even be one that was thought of!) For example, maybe somebody sitting near me at the ball game had a sore throat and passed it on to me.
Hypotheses should be testable by experimentation and deductive reasoning. For example, throat culture and other tests yielded no signs of a bacterial or viral infection, I have no fever or other signs/symptoms, and the doctor says my vocal cords are “swollen” in a way that would indicate overuse.
Hypotheses can be proven wrong/incorrect, but can never be proven or confirmed with absolute certainty. It is impossible to test all given conditions, and someone with more knowledge, sometime in the future, may find a condition under which the hypothesis does not hold true.