一 (yī): The number “one”; signifies a whole, a single, or the entirety.
生 (shēng): Means “life,” “to be born,” or “to live.”
一 (yī): “One” is repeated for emphasis and rhythm.
世 (shì): Means “world,” “era,” or “lifetime.” In this context, it specifically refers to one's existence or lifetime.
When combined, “一 (one) 生 (life) 一 (one) 世 (lifetime)” literally means “one life, one lifetime.” The structure creates a powerful poetic statement: this one life I have, for this one lifetime I've been given, is dedicated to you.