yǔ yán xué jiā / tōng guò / bǐ jiào / Yìn Ōu yǔ / de / gòng tóng / cí gēn / tuī cè / tā men / zài / hěn jiǔ yǐ qián / yǒu / gòng tóng / zǔ yǔ

语言学家通过比较印欧语的共同词根，推测它们在很久以前有共同祖语。

By comparing the common roots of Indo-European languages, linguists infer that they had a common ancestral language long ago.