Sweater

A sweater (American English) is a knitted garment intended to cover the torso and arms. A sweater is either a pullover or a cardigan, distinguished in that cardigans open at the front while pullovers do not. In British English, a pullover may also be called a jumper or jersey, and there is no hypernym equivalent to sweater covering both pullovers and cardigans.

Sweaters are worn by adults and children of all genders; often over a shirt, blouse, T-shirt, or other top, but sometimes next to the skin. Sweaters were traditionally made from wool, but can now be made of cotton, synthetic fibers, or any combination thereof. Sweaters are maintained by washing or dry cleaning, and the use of a lint roller or pill razor.

Types and design

The term "sweater" is a catch-all for a variety of knit garments. Although the term often refers to a pullover, it can also refer to a cardigan, a garment that opens and fastens down the front. Within either group, there is a great variety of design. Various necklines are found, although the V-neck, turtleneck and the crew neck are the most popular. The waistline is typically at hip height or slightly longer, just overlapping the waist of one's pants or skirt, but can vary significantly. It can range from just below the bust in women's garments to mid-thigh in either sex, or even longer in a knitted variation of the poncho shirtdress. The sleeve length is also variable, ranging from full-length or three-quarters to short-sleeved, cap sleeves or sleeveless. The front seam or opening of a cardigan allows for further different styles, such as a surplice or a bolero jacket. All hems may have various types of borders, such as picots, ribbing and frills.

Cave

A cave or cavern is a hollow place in the ground, especially a natural underground space large enough for a human to enter. Caves form naturally by the weathering of rock and often extend deep underground. The word cave can also refer to much smaller openings such as sea caves, rock shelters, and grottos.

Speleology is the science of exploration and study of all aspects of caves and the cave environment. Visiting or exploring caves for recreation may be called caving, potholing, or spelunking.

Types and formation

The formation and development of caves is known as speleogenesis. Caves are formed by various geologic processes and can be variable sizes. These may involve a combination of chemical processes, erosion from water, tectonic forces, microorganisms, pressure, and atmospheric influences.

It is estimated that the maximum depth of a cave cannot be more than 3,000 metres (9,800 ft) due to the pressure of overlying rocks. For karst caves the maximum depth is determined on the basis of the lower limit of karst forming processes, coinciding with the base of the soluble carbonate rocks.