In words ending in -on adopted from French in Middle English, the spelling -on was retained in English （pronounced /（ə）n/, as the last syllable in button）, reflecting a shift of stress away from this final syllable. Words borrowed during the 16th-18th centuries retained the stress on the final syllable with the spelling -oon （pronounced /ˈuːn/, as in balloon）. Later borrowings have tended to retain the French spelling -on （e.g.carton）.