The word "equanimity'' refers to mental calmness, stability, or composure, especially in difficult situations.
Step 1: Analyze the options:
- "Strict'': means firm or harsh in discipline — not related to mental calmness.
- "Composure'': means the state of being calm and in control — a direct synonym.
- "Silent'': refers to not speaking — may seem related but doesn’t reflect inner calmness.
- "Symmetry'': refers to balanced proportions — unrelated to emotional state.
Thus, the correct synonym for "equanimity'' is "composure''.