HTC went out and threw a curve ball by launching a smartphone no one was expecting. A couple of weeks after we were treated to the proper flagship HTC 10, we now have the One S9. A unit less than the current top-end number, the new smartphone also gets to keep the One moniker, joining the One M9, A9, E9, X9, with a plus here and there and a Supreme Camera on top. As a member of the previous generation it also has similar styling to the M9 - the bold chamfer on the 10's back is nowhere to be found. In fact, it's very much impossible to tell the S9 apart from the M9 by looking at two...
Source: http://www.gsmarena.com/the_one_lives_on__htc_one_s9_is_official_with_a_5inch_fullhd_display_and_helio_x10_soc-news-17959.php