Five grains were originally called five kinds of grains in China in ancient times, and later they generally referred to food crops, so there is a saying that "five grains are abundant". There are two main contents. In addition to the five grains, there are also six grains and nine grains. The reason why the five grains theory prevails may be related to the prosperity of the five elements thought.
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There are four articles devoted to agriculture in the famous book Lu's Spring and Autumn Annals in the Warring States Period (works in the third century BC), among which the article "Reviewing the Time" talks about the cultivation of six crops: millet, millet, rice, hemp, rice and wheat. The crops mentioned in the "Twelve Dynasties" article are also these six kinds. In modern botany, it is also said that grains refer to the five categories of crops: spike, hanging, vine, horn and root.