And stop abusing the definition!
Theres no difference between Theory and Theory you say? How about this: Gay meant person prefers same sex people over opposite sex. But it also means happy. You can literally say "I knew a really gay gay person." and it would be a proper English sentence.
So that blows up the argument that word always means the same to everyone out the water. What's next? Ah the definations...
Now, I'll start off with common meaning of the word "Theory". Basically, it's just a guess. "My theory is that this gas tube is kinda bent and blocked the gas flow." That kind of usage. Nothing rock-hard or even a solid guess. If it was something more solid, it would be called educated guess.
Now... in scientific community, it have quite a different meaning. But first, I need to show progression for science to show it's usage.
First, for example, you find out that certain rocks can attract metal. (magnetic, but suppose it's undiscovered...)
You figure out the common actions and effects from this strange rock. You put forth a "Scientific Law" about it.
Now, Scientific Law is the most least stage of the scientific progression. It's nothing but observations and explanation on what happens. Nothing on "WHY" or even a guess on why it does that. However, it must be proven and agreed that it happens.
You and group of scientists has been researching this strange rock and think that it may be a new force, one that attracts metals has has opposing forces. You guys put forth a "Hypothesis" on why it happens. *Note, I'm glossing it over. It's actually more complex than that.*
Now, Hypothesis is the second stage. Generally, it is a Scientific law with something added to it. To be short, to be a Hypothesis, it needs something that try to explain the reasons on this Scientific law. Also, it must be something that may be proven or not. You cannot attribute it to "spirits pulling the metal toward it's home".
Your Hypothesis on this new force, now named Magnetic force, have been proven by other scientists again and again, and the explanation seems to stand to all kinds of experiments and lab set-ups. Apparently it can now be called "Theory of Magnetic force". Congrats!
The Theory, based on scientific usage, is basically a Hypothesis that has been proven over and over and over. In fact, it have stood to pretty lot of scientists. I don't mean a single group of scientists either. I meant many independent groups of scientists has worked on this and they agreed that the Theory stands.
For better explanation and some more details, read the external link.