‘Yù chéng’ is a formal, honorific verb meaning 'to help bring something to successful completion' — especially when expressing gratitude for someone’s generous assistance, guidance, or support in achieving an important goal. Literally, 玉 (yù) means 'jade', symbolizing preciousness, purity, and nobility; 成 (chéng) means 'to succeed' or 'to accomplish'. Together, the phrase evokes the idea of 'polishing something precious until it reaches perfection', suggesting that the helper’s contribution was both noble and essential to the outcome.

This expression is commonly used in written communication — such as thank-you letters, formal speeches, or ceremonial remarks — and almost always appears with a subject who is highly respected (e.g., a mentor, senior official, or benefactor). It is never used for oneself ('I yù chéng you') but rather to acknowledge another’s gracious role in one’s success. Because of its elevated register, it is rarely heard in casual daily speech.