One-word substitution (self-sacrifice for a cause): Choose the term that precisely denotes a person who willingly sacrifices his or her life for a principle, faith, or cause. Context: The word is commonly used in history, religion, and civil rights narratives. Instruction: Select the most accurate single-word substitute.

Given data

• Definition: One who sacrifices life for a cause.
• Domain usage: historical, religious, social justice contexts.

Concept / Approach
A martyr is someone who suffers death rather than renounce a belief or cause. Other terms can involve service or struggle but do not require dying for the cause.

Option analysis
Martyr — death for principle/cause. ✅Patriot — loves/defends country; may or may not die. ❌Revolutionary — advocates change; not necessarily self-sacrifice unto death. ❌Soldier — military role; bravery may involve risk but not inherently martyrdom. ❌

Example
Historical figures executed for beliefs are called martyrs.

Final Answer
Martyr