What is humanity’s greatest invention without which civilizations would collapse?

Apparently sliced bread.

The transistor. Without transistors there will be no tiny computers or cell phones.

Railroads.

I’m going to guess the wheel .

Language.

Civilization: “the stage of human social and cultural development and organization that is considered most advanced”

Many inventions may be basic to the life of an individual, a family, or a community, but civilization crosses those boundaries. I don’t think such a structure or its components can be sustained without a high level of verbal communication.

Agriculture

What Jeruba said. It deserves repeating. All the others are meaningless without it. Imagine someone handing you a wheel while unable to tell you what it is, and you unable to ask about it.

“Collapse”? Hmm, cement.

@stanleybmanly , It is unclear the extent to which we are pre-wired to develop language. There is no place in the world that is without language. It could be that people without any language would spontaneously create one. By way of contrast, we are not born with a disposition for counting. There are languages that do not have words for numbers greater than three.