tyranny of the majority

The idea that in any society where the people have some control and influence on the members of the government, eventually the majority will begin to put people in that government that try to gain more power and freedom for that majority, while marginalizing and persecuting the minorities. That it is impossible to have a place with freedom for everyone equally when there are unequal numbers of groups.

Not as big a problem in modern democracy as some people would have you think. This is so for two reasons.

First, democracy is built on the principle of one man, one vote (or, more contemporarily, "one person, one vote"). This means that a member of any particular (political) minority has just as much power to cast votes and influence lawmakers as a member of the majority. It may seem unfair that a majority can impose their will on a minority. But there is no better way to decide on laws, so long as individual members of the majority have no special power to do so.

Second, when the above fails, the justice system exists. Ideally, the courtroom offers a chance for individuals to contest laws passed by the majority, speak their voice on them, and have the laws overturned if justice requires. In real life, of course, there are unjust decisions and partial judges, but the appeal system is in place to help prevent this.

Overall, you can't do much better where representative government is concerned. If the political majority is always deemed "tyrannical" because of the way their votes work, then an individual or a small minority would be expected to get their way all the time -- and that would lead to simple anarchy in a very short period of time.