# Pipe invert and obvert: Why is it called invert?

In civil engineering, the words invert and obvert are used in the context of pipe elevations. I gather that invert means: interior bottom elevation of pipe, and obvert means: interior top elevation of pipe.

However, using the word invert in this context seems strange to me. To me, none of these definitions fit:

Invert (Merriam-Webster)

1. a: to reverse in position, order, or relationship
b: to subject to inversion
2. a: to turn inside out or upside down
b: to turn inward
3. a: to find the mathematical reciprocal of
b: to divide using fractions, invert the divisor and multiply

What does the word invert have to do with pipes? What has been inverted?

• Ultimately, it's jargon. Apr 7, 2017 at 21:45
• Nothing wrong with jargon: we even have a tag for it. By all means edit it in if that tag is appropriate here. I'm not sure it is (but then I trained as an engineer, so whether it's jargon or not may be difficult to determine). Apr 7, 2017 at 22:31
• @AndrewLeach I just tried, but it didn't take effect. It appears to already be categorized as a tag synonym of terminology, which the question already had. Apr 7, 2017 at 23:12
• This online dictionary actually has the best explanation: dictionary.com/browse/ob- [...]but now used also, with the sense of “reversely,” “inversely,” to form Neo-Latin and English scientific terms: object; obligate; oblanceolate. If you take invert and obvert together, the obvert is the reverse of the invert. Apr 8, 2017 at 16:36
• The inverted arch thing would make even more sense to me if, historically, pipes were just trenches/inverted arches/channels, and not tubular. Apr 8, 2017 at 16:38