信xìn 是shì 朋友péngyou 写xiě 的de。xìn shì péngyou xiě de.The letter was written by a friend.Breakdown of xìn shì péngyou xiě de.是shìshìto be朋友péngyoupéngyoufriend写xiěxiěto write的dedestructural particleElon.io is an online learning platformWe have an entire course teaching Chinese grammar and vocabulary.Start learning Chinese now