 a baby bottle is a bottle with a teat (also called a nipple in the us) to drink directly from. it is typically used by infants and young children when a mother does not breastfeed, or if someone cannot (as conveniently) drink from a cup, for feeding oneself or being fed. in particular it is used to feed infant formula, expressed breast milk or pediatric electrolyte solution. ==dimensions and design== a large-sized bottle typically holds 280 ml; the small size 150 ml. it is composed of a bottle itself, a teat, a ring to seal the teat to the bottle, a cap to cover the teat and optionally a disposable liner. the height-to-width ratio of bottles is high (relative to adult cups) because it is needed to ensure the contents flood the teat when used at normal angles; otherwise the baby will drink air. however, if the bottle is too tall, it easily tips. there are asymmetric bottles that ensure the contents flood the teat if the bottle is held at a certain direction. ===teats (or nipples)===  the teat itself is generally designed to be slimmer than the mother's nipple. specialized teats are marketed that report attempting to mimic the shape of the breast to help babies to switch back and forth between bottle feeding and breastfeeding for cases where "nipple confusion" occurs.http://www.askdrsears.com/topics/breastfeeding/common-problems/nipple-confusion  teats come in a selection of flow rates, marketed to be based on the age of the infant. different flow rate teats either have more holes or larger holes. variable flow rate teats are available for older infants. the hole is asymmetric so that by turning the bottle/teat, different flows can occur. specialized teats are available for infants with cleft palate. ===vented bottles=== "vented" bottles allow air to enter the bottle while the baby is drinking without the need to break the baby's suction during feeding. alternatively a bottle liner can be used to enclose the formula instead of directly in the bottle. the liner collapses as the formula is drained. vented bottles work by allowing air to enter while preventing the liquid inside from escaping. avent is a popular brand in this category in the united states. it works by an "anti-vacuum skirt" in the base of the teat, where it forms a seal with the bottle. the skirt acts as a one way valve, allowing air to enter the bottle but not liquids to leave. if the sealing ring is tightened too much, the skirt is compressed too tightly to allow it to open and the bottle will not vent. if the s
Bottles Infant_feeding