zuò / jiǔ / le / yǐ / hòu / tā / de / wěi / jǐ / gǔ / kāi / shǐ / yǐn / yǐn / zuò / tòng坐久了以后,他的尾脊骨开始隐隐作痛。After sitting for a long time, his tailbone began to ache slightly.