anh

Etymology
From.

According to Phan Kế Bính's Việt Nam phong tục (1915), apparently the practice of calling each other anh- for those in relationship originated from the province of Quảng Nam:

Noun

 * 1) an
 * 2) a male cousin who's descended from an ancestor who is/was an older sibling to yours or your spouse's
 * 3)  a generic thing
 * 1)  a generic thing

Pronoun

 * 1) I/me, your male cousin who's descended from an ancestor who is/was an older sibling to yours or your spouse's
 * 2) I/me, your  older than you
 * 3)  I/me, your
 * , a male who's (presumably) slightly older than me
 * 1) you, my male cousin who's descended from an ancestor who is/was an older sibling to mine or my spouse's
 * 2) you, my boyfriend
 * 3) you, my husband
 * 4)  you, the high schoolboy reading this textbook
 * , that young adult man
 * 1) you, my male cousin who's descended from an ancestor who is/was an older sibling to mine or my spouse's
 * 2) you, my boyfriend
 * 3) you, my husband
 * 4)  you, the high schoolboy reading this textbook
 * , that young adult man
 * 1) you, my boyfriend
 * 2) you, my husband
 * 3)  you, the high schoolboy reading this textbook
 * , that young adult man
 * 1)  you, the high schoolboy reading this textbook
 * , that young adult man
 * 1)  you, the high schoolboy reading this textbook
 * , that young adult man
 * 1)  you, the high schoolboy reading this textbook
 * , that young adult man
 * , that young adult man
 * , that young adult man

Usage notes
Textbooks tend to assume grade schoolers and middle schoolers to be young enough to be called, but high schoolers to be old enough to be called and. The "pronoun" choices for high schoolers in these books are strictly binary, and the female is always secondary and shown in parentheses.