A sith law making it so that there can never be more than two active sith at one time, one master, and one pupil. The rule was set in place by Darth Bane after he killed all the other sith.(Darth bane also started the tradition of prefixing sith names with "darth")
Darth Sideous only ever had one deciple at a time, first Darth Maul, then Darth Tyranus, then Darth Vader. Although he surounded himself with other Dark Jedi, there were only ever two Sith at one time, in accordance with the Rule Of Two.
This term is a universal rule of probability. The rule states that whenever there is a picture on a dating app that contains two girls, with one of them being significantly more attractive than the other, the person whose profile you're swiping is the less attractive of the two.
When I saw Isabella pictures on Tinder I got excited when I thought she was the hot girl on the right....turns out I fell victim to the Tinder Rule of Two.
A hardo is a person who tries extremely hard at everything. Most times a hardo will try very hard at things that do not require excessive effort. For example, sports practices, gym class, etc.
Wow did you see Jack at practice today? What a hardo!