He and I are nothing more than nodding acquaintances; we're not close.
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Literary phrase - 颔首 (hànshǒu, to nod) is a classical word for 'nod', much more formal than the everyday 点头 (diǎntóu). Use this in writing or thoughtful speech, not casual chat.
culture
Chinese has a graded vocabulary for friendship intensity: 莫逆之交 (sworn friends), 知己 (true confidant), 朋友 (friend), 熟人 (familiar person), 颔首之交 (nodding acquaintance), 点头之交 (the same in plainer style).
