Final answer:
A synonym for 'selfless' is 'altruistic', relating to the concept of altruism, which means having a selfless concern for the well-being of others, often expressed through generous and compassionate actions.
Step-by-step explanation:
A synonym for 'selfless' is 'altruistic'. This word refers to a person's ability to be concerned for the wellbeing of others without any regard for one's own interests. It is derived from the concept of altruism, which is the selfless care for others' well-being. When someone is described as altruistic, they often display characteristics like generosity, empathy, and compassion. An example of altruistic behavior would be someone donating time or money to help those in need, without seeking recognition or reward for their actions. In the excerpt provided from Fronto to Lucius Verus, qualities akin to altruism are highlighted, particularly the Roman virtue of warmth of affection, indicating a caring and selfless disposition.