facet
One side or aspect of something complex or many-sided.
A facet is one aspect or part of something larger and more complex. Think of your best friend: you might know their funny side, their serious side when they're worried about something, their competitive side in soccer, and their creative side in art class. Each of these is a different facet of who they are.
The word comes from gemstones, where each flat, polished surface cut into a diamond or ruby is called a facet. A well-cut diamond might have dozens of facets, and each one catches the light differently. When you look at the whole gem, you're seeing all those facets working together to create something beautiful and brilliant.
This makes facet perfect for describing complicated things that have many sides to them. A difficult problem might have legal facets, scientific facets, and ethical facets. A historical event like the American Revolution has military facets, economic facets, and philosophical facets. When your teacher asks you to consider all facets of an issue, she wants you to look at it from every angle and examine each different aspect carefully.
Unlike words like “part” or “piece,” facet suggests something that adds depth and interest to the whole. Each facet makes the complete picture more nuanced and worth exploring.