On the 27th of March of 2015, I first encounter now the word "tetragram." It is apparently any square-shaped symbol of a complex writing system in the Sinosphere. A sinogram, or sinograph, is a tetragram. It is my first time of learning that term. "Tetra" means four. Japanese Kana are tetragrams, as well as Korean Hangeul, because they are square-shaped, too.
Source: tatoeba (10713870)