Is it called yam in English?

Or sweet potato.

Yams and sweet potatoes are different vegetables. What are called 'yams' in the USA are actually a variety of sweet potato. Why the confusion? In the United States, firm varieties of sweet potatoes were produced before soft varieties. When soft varieties were first grown commercially, there was a need to differentiate between the two. African slaves had already been calling the ‘soft’ sweet potatoes ‘yams’ because they resembled the true yams in Africa. Thus, ‘soft’ sweet potatoes were referred to as ‘yams’ to distinguish them from the ‘firm’ varieties. China is the world's largest sweet potato producing country in terms of acreage and production volumes.

Looks like a sweet potato to me 😆

Wikipedia
Although the soft, orange sweet potato is often called a "yam" in parts of North America, the sweet potato is botanically very distinct from a genuine yam (Dioscorea), which is native to Africa and Asia and belongs to the monocot family Dioscoreaceae. To add to the confusion, a different crop plant, the oca (Oxalis tuberosa, a species of wood sorrel), is called a "yam" in many parts of Polynesia, including New Zealand. The United States Department of Agriculture requires that the label "yam" always be accompanied by "sweet potato" in U.S. retail sales of sweet potato.[6]

Although the sweet potato is not closely related botanically to the common potato, they have a shared etymology. The first Europeans to taste sweet potatoes were members of Christopher Columbus's expedition in 1492. Later explorers found many cultivars under an assortment of local names, but the name which stayed was the indigenous Taino name of batata. The Spanish combined this with the Quechua word for potato, papa, to create the word patata for the common potato.

In Argentina, Venezuela, Puerto Rico and the Dominican Republic the sweet potato is called batata. In Mexico, Peru, Chile, Central America, and the Philippines, the sweet potato is known as camote (alternatively spelled kamote in the Philippines), derived from the Nahuatl word camotli.[7]

In Peru, the Quechua name for a type of sweet potato is kumar, strikingly similar to the Polynesian name kumara and its regional Oceanic cognates (kumala, umala, 'uala, etc.), which has led some scholars to suspect an instance of pre-Columbian trans-oceanic contact.

In New Zealand, the most common cultivar is the red (purple) cultivar called kumara, a name derived from the Māori name kūmara, but orange ('Beauregard') and gold cultivars are also available.[8] Kumara is particularly popular as a roasted food, or in contemporary cuisine as kumara chips, often served with sour cream and sweet chili sauce. Occasionally, shops in Australia will label purple cultivars as "purple sweet potato" to denote the difference to the other cultivars. About 95% of Australia's production is of the orange cultivar named 'Beauregard', originally from North America, known simply as "sweet potato". A reddish-purple cultivar, 'Northern Star', is 4% of production and is sold as "kumara".

Origin, distribution and diversity[edit]
The origin and domestication of sweet potato is thought to be in either Central America or South America.[9] In Central America, sweet potatoes were domesticated at least 5,000 years ago.[10] In South America, Peruvian sweet potato remnants dating as far back as 8000 BC have been found.

One author postulated that the origin of I. batatas was between the Yucatán Peninsula of Mexico and the mouth of the Orinoco River in Venezuela.[11] The 'cultigen' had most likely been spread by local people to the Caribbean and South America by 2500 BC.[12] Strong supporting evidence was provided that the geographical zone postulated by Austin is the primary center of diversity.[11] The much lower molecular diversity found in Peru–Ecuador suggests this region should be considered as a secondary center of sweet potato diversity.

The sweet potato was grown in Polynesia before western exploration. Sweet potato has been radiocarbon-dated in the Cook Islands to 1000 AD, and current thinking is that it was brought to central Polynesia around 700 AD, possibly by Polynesians who had traveled to South America and back, and spread across Polynesia to Hawaii and New Zealand from there.[13][14] It is possible, however, that South Americans brought it to the Pacific, although this is unlikely as it was the Polynesians who had a strong maritime tradition and not the Native South Americans. The theory that the plant could spread by floating seeds across the ocean is not supported by evidence. Another point is that the sweet potato in Polynesia is the cultivated Ipomoea batatas, which is generally spread by vine cuttings and not by seeds.[15]

Sweet potatoes are cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth.[16] Due to a major crop failure, sweet potatoes were introduced to Fujian province of China in about 1594 from Luzon. The growing of sweet potatoes was encouraged by the Governor Chin Hsüeh-tseng (Jin Xuezeng).[17][18] Sweet potatoes were introduced as a food crop in Japan, and by 1735 were planted in Shogun Tokugawa Yoshimune's private garden.[19] It was also introduced to Korea in 1764.[20]

Sweet potatoes became popular very early in the islands of the Pacific Ocean, spreading from Polynesia to Japan and the Philippines. One reason[original research?] is that they were a reliable crop in cases of crop failure of other staple foods because of typhoon flooding. They are featured in many favorite dishes in Japan, Taiwan, the Philippines, and other island nations. Indonesia, Vietnam, India, and some other Asian countries are also large sweet potato growers. Sweet potato, also known as kelang in Tulu, is part of Udupi cuisine in South India. Uganda (the second largest grower after China), Rwanda, and some other African countries also grow a large crop which is an important part of their peoples' diets. The New World, the original home of the sweet potato, grows less than three percent (3%) of the world's supply. Europe has only a very small sweet potato production, mainly in Portugal. In the Caribbean, a cultivar of the sweet potato called the boniato is popular. The flesh of the boniato is cream-colored, unlike the more popular orange hue seen in other cultivars. Boniatos are not as sweet and moist as other sweet potatoes, but many people prefer their fluffier consistency and more delicate flavor.

Sweet potatoes have been an important part of the diet in the United States for most of its history, especially in the Southeast. From the middle of the 20th century, however, they have become less popular. The average per capita consumption of sweet potatoes in the United States is only about 1.5–2 kg (3.3–4.4 lb) per year, down from 13 kg (29 lb) in 1920. Southerner Kent Wrench writes: "The Sweet Potato became associated with hard times in the minds of our ancestors and when they became affluent enough to change their menu, the potato was served less often."[21]

Transgenicity[edit]
A study published in 2015 by scientists from Ghent University and the International Potato Center found that the genome of cultivated sweet potatoes contains sequences of DNA from Agrobacterium, with genes being actively expressed by the plants. The discovery of the transgenes was made while performing metagenomic analysis of the sweet potato genome for viral diseases. Transgenes were observed both in the sweet potato's closely related wild relatives, and also were found in more distantly related wild species. This observation makes cultivated sweet potatoes the first known example of a naturally transgenic food crop.[22][23]

I've had both yams and sweet potatoes, and they are very different.

Sweet potatoes, as the name implies are sweet.

Yams are very starchy tasting, and not at all sweet.

I live in a district of a British city where there is a community of West Indies background, and many of the corner stores sell both yams and sweet potatoes. You soon learn the difference.