"Big", "Large" and "Great" are abstract concepts, but the ancient Chinese writers were able to use a simple picture to communicate these concepts. The oracle script illustrates an individual standing with legs apart and arms spread out, similar to someone standing large to display prowess.
Many Chinese words use 大 as a radical. Some words use 大 as a radical on top: 奇 (special)，奔 (run). Other characters use it on the bottom: 夫 (husband), 天 (heaven)，尖 (sharp).