使用了系表结构来定义友谊的性质，表达简洁有力。
Friendship is the most precious thing in the world, and deep friendship is one of life's greatest comforts. ——Zou Taofen
Friendship is the seasoning of life and also the medicine that relieves life's pain. ——Emerson
Friendship is the best school for cultivating human emotions.
Friendship is a school that nurtures human feelings. We need friendship not to simply pass the time, but to cultivate virtues in others and in ourselves. ——Sukhomlinsky
Friendship is a school that cultivates human feelings. ——Sukhomlinsky
Friendship is a means of virtue, and friendship itself is a virtue, a shared virtue. ——Feuerbach
Friendship is the union of souls. This union can be separated, and it is an unspoken agreement between two sensitive and honest people. ——Voltaire
Friendship is when two hearts treat each other sincerely, not when one heart strikes against another. ——Lu Xun
Friendship is a selfless relationship between two equals; love, however, is a humble exchange between a tyrant and a slave. ——Oliver Goldsmith
友谊是天地间最可宝贵的东西，深挚的友谊是人生最大的一种安慰。 ——邹韬奋
友谊是人生的调味品，也是人生的止痛药。 ——爱默生
友谊是培养人感情最好的学校。
友谊是培养人的感情的学校。我们所以需要友谊，并不是想用它打发时间，而是要在人身上，在自己的身上培养美德。 ——苏霍姆林斯基
友谊是培养人的感情的学校。 ——苏霍姆林斯基
友谊是美德之手段，并且本身就是美德，是共同的美德。 ——费尔巴哈
友谊是灵魂的结合，这个结合是可以离异的，这是两个敏感，正直的人之间心照不宣的契约。 ——伏尔泰
友谊是两颗心真诚相待，而不是一颗心对另一颗心敲打。 ——鲁迅
友谊是两个平等者之间的无私交往；爱情则是暴君与奴隶之间的卑下交流。 ——奥立弗·哥尔斯密