You are all arrogant twits. I have several times tried to explain to you what the terms parallel and vertical twin is about, but you will hear none of it and rely solely on your own "expertise". You know, there was a time BEFORE the internet, and therefore NOT ALL information is available herein. Maybe. I found some information on the subject, but you just pretend its not there. Why? You know that JUST BECAUSE SOMETHING IS NOT WRITTEN IN ENGLISH DOES NOT MEAN ITS NOT THERE!!! It SHOULD ring a bell that your explanation of the terms could apply to ALL engines, but it doesnt. They are used ONLY on twin cylinder engines. Why is this? Its because YOU are WRONG my dear fellas. You are just too cowardy or xenophobic to admit that some Scandinav knew something you didnt. 

 Thank you.