Sustain most nearly means?

The term "sustain" most closely aligns with the idea of maintaining something over time or keeping it in existence. When we talk about sustaining, we often refer to the ability to preserve or prolong a condition, situation, or resource. This is why "maintain" is the most accurate synonym in this context.

For instance, when we say we need to sustain our environment, we mean that we must maintain its health and resources so they continue to exist for future generations. Sustaining a project involves keeping it going and ensuring its continuous operation, which is encapsulated perfectly by the word "maintain."

On the other hand, while "endure" and "tolerate" suggest dealing with something challenging or uncomfortable, they do not convey the ongoing aspect of keeping something in existence or operational. "Support" can imply assistance but does not inherently involve the concept of continuation or maintaining a state over time. Thus, "maintain" is the term that best represents the concept of sustaining.