Constitutionality is whether something is acceptable according to a constitution. When people talk about “the constitutionality of a new law,” they are asking: does this law fit the constitution, or does it break it? If a court finds a serious problem of constitutionality, it may say the government cannot use that law. The word is technical and legal. In Taiwan you will hear it around the Constitutional Court. It is not a question of whether a law is wise, kind, or popular — only whether it matches the constitution. Though actually, in political fights people sometimes shout “unconstitutional!” as a strong complaint before any court has spoken; that is rhetoric, not a ruling.