Derived measures
air changes per hour (ACH), a measure of the replacements of air within a defined space used for indoor air quality
ampere hour (Ah), a measure of electrical charge used in electrochemistry
BTU-hour, a measure of power used in the power industry and for air conditioners and heaters
credit hour, a measure of an academic courses contracted instructional time per week for a semester
horsepower-hour (hph), a measure of energy used in the railroad industry
hour angle, a measure of the angle between the meridian plane and the hour circle passing through a certain point used in the equatorial coordinate system
kilometres per hour (km/h), a measure of land speed
kilowatt-hour (kWh), a measure of energy commonly used as an electrical billing unit
knot (kn), a measure of nautical miles per hour, used for maritime and aerial speed
man-hour, the amount of work performed by the average worker in one hour, used in productivity analysis
metre per hour (m/h), a measure of slow speeds
mile per hour (mph), a measure of land speed
passengers per hour per direction (p/h/d), a measure of the capacity of public transportation systems
pound per hour (PPH), a measure of mass flow used for engines fuel flow
work or working hour, a measure of working time used in various regulations, such as those distinguishing part- and full-time employment and those limiting truck drivers working hours or hours of service

See also
Liturgy of the Hours
Horology
Horae, the deified hours of ancient Greece and Rome
Hexadecimal hour, a proposed unit lasting 1 h 30 min
Decimal hour or deciday, a French Revolutionary unit lasting 2 h 24 min
Golden Hour & Blue Hour in photography
Metric time

Notes
References
Bibliography
Further reading
Gerhard Dohrn-van Rossum (1996).
Retained placenta is a condition in which all or part of the placenta or membranes remain in the uterus during the third stage of labour. Retained placenta can be broadly divided into:

failed separation of the placenta from the uterine lining
placenta separated from the uterine lining but retained within the uterusA retained placenta is commonly a cause of postpartum haemorrhage, both primary and secondary.Retained placenta is generally defined as a placenta that has not undergone placental expulsion within 30 minutes of the baby’s birth where the third stage of labor has been managed actively. Signs and symptoms
Risks of retained placenta include hemorrhage and infection. After the placenta is delivered, the uterus should contract down to close off all the blood vessels inside the uterus. If the placenta only partially separates, the uterus cannot contract properly, so the blood vessels inside will continue to bleed. A retained placenta thereby leads to hemorrhage. Management
Drugs, such as intraumbilical or intravenous oxytocin, are often used in the management of placental retention. It is useful ensuring the bladder is empty. However, ergometrine should not be given as it causes tonic uterine contractions which may delay placental expulsion. Controlled cord traction has been recommended as a second alternative after more than 30 minutes have passed after stimulation of uterine contractions, provided the uterus is contracted. Manual extraction may be required if cord traction also fails, or if heavy ongoing bleeding occurs.