watertight：不透水的，防水的；严密的，无懈可击的 

词根词缀：water水 + -tight紧的→密不透…的

• maternity
• maternity leave
• mateship
• matey
• math
• mathematician
• mathematics
• Matilda
• matinee
• matinee idol
• mating
• matins
• matri-
• matriarch
• matriarchal
• matriarchy
• matric
• matric exemption
• matricide
• matriculate
• matrilineal
• matrimonial
• matrimony
• matrix
• matron