【朋友多了路好走】

buddy/pal哥们儿;
pen pal笔友;
confidante闺蜜/红颜知己;
fellow-townsman老乡;
fair-weather friend酒肉明友;
bad company狐朋狗友;
comrade-in-arms战友;
schoolmate同窗;
alumnus男校友;
alumna女校友;
fellow-apprentice师兄(弟);
sworn brother结拜兄弟;