directrices

directrices is a technical plural noun you are most likely to meet in geometry, where it means fixed reference lines used to define conic sections such as parabolas, ellipses, and hyperbolas. The singular form is directrix, and the word often appears alongside focus because the curve is described through a distance relationship between a point, a focus, and a line. But there is a useful nuance: directrices is not always just “more than one line” in casual wording, and it also has a rare, historical person meaning connected to female directors. When should you think geometry, and when is another meaning possible? Watch the full lesson to learn the word clearly.