好友 literally combines 好 (hǎo, 'good') and 友 (yǒu, 'friend'), meaning a close, trusted, or long-standing friend — someone you share mutual respect, affection, and frequent contact with. Unlike the more general term 朋友 (péngyou), which covers acquaintances and casual friends, 好友 implies emotional closeness and reliability.

This word is commonly used in both spoken and written Chinese, especially when emphasizing depth of relationship — for example, when introducing someone important in your life, writing heartfelt messages, or describing shared experiences like studying abroad or overcoming challenges together. It carries a warm, positive connotation and is appropriate in neutral to formal registers, though it’s less common in highly formal documents than terms like 挚友 (zhìyǒu, 'dear friend').