One answers why, the other answers how, and never the twain should meet, he said.
From the kansas.com
There are winter folk, and there are summer folk, and never the twain shall meet.
From the guardian.co.uk
Twain was fascinated, puzzled and eventually resolved about the nature of humans.
From the bostonherald.com
Twain was born two weeks after the closest approach to Earth of Halley's Comet.
From the en.wikipedia.org
Twain was guilt-stricken and held himself responsible for the rest of his life.
From the en.wikipedia.org
Twain doesn't make an appearance in Holbrook's autobiography until that point.
From the sfgate.com
Twain supported the accessibility of books to everyone from all walks of life.
From the guardian.co.uk
Twain made a second tour of Europe, described in the 1880 book A Tramp Abroad.
From the en.wikipedia.org
Twain knew instinctively how well the form suits a restless, dynamic country.
From the economist.com
More examples
Couple: two items of the same kind
TWAIN is a standard software protocol and applications programming interface (API) that regulates communication between software applications and imaging devices such as scanners and digital cameras.
Is a scanning interface standard developed to address the need for consistent, easy integration of scanners with document imaging programs. Software programs that are written to support the TWAIN standard are capable of controlling any TWAIN compliant scanner.
A standard developed to allow imaging devices such as scanners and digital cameras to communicate with PCs.
TWAIN is a standard for getting input from image scanners: an image capture API for Microsoft Windows and Apple Macintosh operating systems. The standard was first released in 1992 and is maintained by the TWAIN Working Group. ...
Had abandoned the work in 1874, but returned to it in the following summer and even then was undecided if he were writing a book for adults or for young readers.
A standard for acquiring images from image scanners, allowing scanning an image directly into the application (such as Photoshop). For some workflows, this is an important optimization.
Technology Without An Interesting Name; the standard interface between software applications and image-capturing devices such as scanners.
Imaging standard used to interface scanners and digital cameras to applications such as Photoshop and other image editors. TWAIN enables the user to scan or download pictures without exiting the image editing program.