一心
いっしん · isshin · JLPT N1 · adverb
one mind
一 — single horizontal stroke
一 is one of the simplest pictographs in Chinese, depicting a single horizontal line to represent the number one. It has retained essentially the same form since oracle bone script over 3,000 years ago. By extension it also means 'first,' 'whole,' or 'same.'
心 — pictograph of a heart with chambers and aorta
心 is a pictograph showing a stylized heart, with strokes representing the organ's chambers and the aorta at the top. Originally meaning the physical heart, it broadened to cover mind, feelings, and intentions, since ancient Chinese thought located thinking and emotion in the heart.