Hordeum vulgare (barley) is a gramineous plant, used primarily as a food and feed crop, and also as a fermentation material for beer and some distilled spirits. Chinese commonly known as March yellow. Barley is the fourth largest cultivated grain in the world, after maize, rice and wheat, with 490,000 square kilometers of barley harvested in 2014 and an annual output of about 144 million tons. By 2016, the annual world production of barley was about 147 million tons.

Barley is a biennial herb. Plant like wheat; Culm hollow soft, about 100 cm high, each tiller 3-6 or more; Leaves alternate slightly thick and short, light color, tongue, ear larger, hairless; Spike, self-pollinating main, each section of the spike bearing three spikelet, each spikelet flower; The spikelet has a pair of glumes, and the floret has an inner and outer glumes, narrow and slender, the outer glumes are larger with or without awning; The inner lemma usually encloses the grain tightly, the lemma is broad and flat, and the apex is awned. Caryopsis has a variety of complex colors.

Barley originated from the wild barley (Hordeum vulgare subsp. spontaneum) that can still be found in the Middle East. Both types of barley are diplosomal (2n=14 chromosomes). There are so many hybrids of all the different kinds of barley that today they are all considered one species. The main difference between barley and its wild variety is the fragile leaf axis produced by the latter due to self-pollination.

The earliest barley was found at Paleolithic sites in the Levant in the eastern Mediterranean. The first domesticated barley appeared in Neolithic Syria. The domestication of barley seems to have occurred at the same time as that of wheat.

The highland barley, a variety of barley, has become the staple food of Tibetan cuisine since the 5th century, and the barley made from its grinding powder is still the staple food of Tibetan people today.

In medieval Europe, tenant farmers ate bread made from barley and rye, while wheat was consumed by the upper classes. Until the 19th century, potatoes largely replaced barley in Eastern Europe.

Barley is highly adaptable and today is one of the main crops in temperate and tropical regions. It is cultivated in north and south China. Barley grows in a wide range of environments and has spring and winter growth habits.