Sum(me:r) is the ninth extended play by South Korean boy group Pentagon.

Pentagon held a live showcase at Blue Square Samsung Card Hall in Hannam-dong, Seoul before the release of the EP on July 17, where they performed "Humph!"

[10][11] The group appeared as guests on JTBC's Run.wav (런웨이브) to promote the album, making their debut on the show.

was released alongside a music video that turns the members of Pentagon into schoolboys part of a baseball club, where they don uniforms featuring the New York Yankees' logo.

Though only eight of Pentagon's nine members appear in the music video, the voice of Yan An, who did not participate in group activities due to an injury, can be heard on the single.