‘写信’ literally means ‘to write + letter’ and functions as a compound verb meaning ‘to write a letter’. The first character 写 (xiě) means ‘to write’, while 信 (xìn) means ‘letter’ or ‘mail’. Together, they form a common, everyday verb used for sending handwritten or formal messages—especially in contexts where digital communication is less appropriate, such as to elders, for official correspondence, or during cultural practices like Lunar New Year greetings.

This verb is typically used with objects (e.g., 写一封信, 写给朋友的信), time expressions (e.g., 昨天写了封信), or aspect particles like 了 or 着. It’s neutral in register—neither formal nor slang—but implies intentionality and effort, distinguishing it from casual texting or emailing. While still taught and understood, its usage has declined with digital communication; however, it remains culturally significant in education, etiquette, and literature.