An udder is an organ formed of the mammary glands of female quadruped mammals, especially ruminants such as cattle, goats, sheep and deer.

The udder is a single mass hanging beneath the animal, consisting of pairs of mammary glands. In cattle there are normally two pairs, in sheep, goats and deer there is one pair, and in some animals such as pigs there are many pairs.

Udder care and hygiene in cows is important in milking, aiding uninterrupted and untainted milk production, and preventing mastitis. Products exist to soothe the chapped skin of the udder.

Ulceration may refer to:

– Ulcer (dermatology), a discontinuity of the skin
– Oral ulcer, an open sore inside the mouth
– Aphthous ulcer, a specific type of oral ulcer also known as a canker sore
– Peptic ulcer, a discontinuity of the gastrointestinal mucosa (stomach ulcer)
– Corneal ulcer, an inflammatory or infective condition of the cornea
– Venous ulcer, a wound thought to occur due to improper functioning of valves in the veins
– Genital ulcer, an ulcer located on the genital area

Urea or carbamide is an organic compound with the chemical formula (NH2)2CO. The molecule has two amine (-NH2) residues joined by a carbonyl (-CO-) functional group.

Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals. Being solid, colourless, odorless, neither acidic nor alkaline, highly soluble in water, and relatively non-toxic, urea is widely used in fertilizers as a convenient source of nitrogen. Urea is also an important raw material for the chemical industry. The synthesis of this organic compound by Friedrich Wöhler in 1828 from an inorganic precursor was an important milestone in the development of chemistry.

The terms urea and carbamide are also used for a class of chemical compounds sharing the same functional group RR’N-CO-NRR’, namely a carbonyl group attached to two organic amine residues. Example include carbamide peroxide, allantoin, and hydantoin. Ureas are closely related to biurets and related in structure to amides, carbamates, diimides, carbodiimides, and thiocarbamides.