When a Youtube video ends, Youtube starts another in less than ten seconds.
(»Next video«, Nächstes Video):
If you do not want that:
Create a playlist, put the video into the playlist, and run the playlist. The URL looks like this:
All in one line, naturally. You are welcome to try.
The »?v=…« is the specific video, the »&list=…« is the playlist, formally.
To create a playlist: Log in to Youtube
Don’t mess with your established paylists, click on »new playlist« (upper right, »Neue Playlist«), and create one at your ease. The name does not matter. Into this playlist place the one video you’d like to show and then stop. Just one video. Mail your friends the link to run this playlist.
Your video will play and then stop. Thank you, Youtube. And don’t you dare to change that!