The main difference between Turnip and Radish is that the Turnip is a root vegetable and Radish is a species of plant.
The turnip or white turnip (Brassica rapa subsp. rapa) is a root vegetable commonly grown in temperate climates worldwide for its white, bulbous taproot. The word turnip is a compound of tur- as in turned/rounded on a lathe and neep, derived from Latin napus, the word for the plant. Small, tender varieties are grown for human consumption, while larger varieties are grown as feed for livestock. In the north of England, Scotland, Ireland, Cornwall and eastern Canada (Newfoundland), turnip (or neep) often refers to rutabaga, a larger, yellow root vegetable in the same genus (Brassica) also known as swede (from "Swedish turnip").
The radish (Raphanus raphanistrum subsp. sativus) is an edible root vegetable of the Brassicaceae family that was domesticated in Europe in pre-Roman times. Radishes are grown and consumed throughout the world, being mostly eaten raw as a crunchy salad vegetable. They have numerous varieties, varying in size, flavor, color, and length of time they take to mature. Radishes owe their sharp flavor to the various chemical compounds produced by the plants, including glucosinolate, myrosinase, and isothiocyanate. They are sometimes grown as companion plants and suffer from few pests and diseases. They germinate quickly and grow rapidly, smaller varieties being ready for consumption within a month, while larger daikon varieties take several months. Another use of radish is as cover or catch crop in winter or as a forage crop. Some radishes are grown for their seeds; daikon, for instance, may be grown for oil production. Others are used for sprouting.
From turnepe, probably from turn + Middle English nepe, from Old English nǣp, from Latin nāpus. The component turn may be due to the round shape of the plant as though turned on a lathe, or because it must be turned and twisted to be harvested. Cognate to neep. See also parsnip.
turnip (plural turnips)
turnip (third-person singular simple present turnips, present participle turniping or turnipping, simple past and past participle turniped or turnipped)
From Middle English radishe, redich, radiche, raddik, radike, redic, from Old English redic, rædic, from Vulgar Latin rādīce, the accusative singular of rādīx (“root of a plant; radish”); later influenced by Anglo-Norman radich, radice, and Middle French radice (modern French radis), from Latin. Cognate with Danish reddike, ræddike, Italian radice, Middle Dutch radic, Old High German ratih, retih (Middle High German retich, modern German Rettich, Rettig), Old Saxon redik (Middle Low German rēdik, reddik, rētik, and other forms), Old Swedish rädikia, rätikia, and other forms (modern Swedish rättika), Portuguese raditz.
radish (plural radishes)