手紙

Refers specifically to a physical message written on paper and sent via mail or messenger. In the modern digital era, "手紙" is strictly distinguished from "メール" (email) or "メッセージ" (instant messages). While emails are for efficiency and speed, "手紙" carries a strong connotation of thoughtfulness, effort, and emotional weight.

Depending on the context, the register can vary significantly. A casual letter to a friend uses informal language, whereas a formal letter (often referred to as "書簡" in academic or highly formal contexts) follows strict etiquette, including specific opening and closing greetings (e.g., "拝啓" and "敬具").

Using "手紙" often implies a slower, more deliberate form of communication, making it a common motif in literature and romance to express deep feelings that are too precious for a digital screen.