regrettable：令人遗憾的，可惜的，可悲的  

词根词缀：regret遗憾,懊悔 + -able形容词词尾

• owl
• owlet
• own
• owner
• ownership
• own goal
• owt
• ox
• oxbow
• Oxbridge
• Oxford
• oxidant
• oxide
• oxidize
• Oxon
• Oxonian
• oxtail
• oxter
• oxy-
• oxyacetylene
• oxyacid
• oxygen
• oxygenate
• oxygenator
• oxymoron