substructure
🇺🇸
/ˈsʌbstrʌktʃər/
🇬🇧
/ˈsʌbstrʌktʃə(r)/
The part of something that is underneath and supports the rest of it.
The bridge has a strong substructure made of concrete.
这座桥有一个由混凝土制成的坚固基础。