The four cardinal directions or cardinal points are the directions of north, east, south, and west, commonly denoted by their initials: N, E, S, W. East and west are at right angles to north and south, with east being in the clockwise direction of rotation from north and west being directly opposite east. Intermediate points between the four cardinal directions form the points of the compass. The intermediate (intercardinal, or ordinal) directions are northeast (NE), southeast (SE), southwest (SW), and northwest (NW). Further, the intermediate direction of every set of intercardinal and cardinal direction is called a secondary-intercardinal direction, the eight shortest points in the compass rose to the right, i.e. NNE, ENE, ESE, and so on.
On Earth, upright observers facing north will have south behind them, east on their right, and west on their left. Most devices and methods for orientation therefore operate by finding north first, although any other direction is equally valid, if it can be reliably located. Several of these devices and methods are described below.
Magnetic declination is the angle between compass north (the direction the north end of a compass needle points) and true north (the direction along the earth's surface towards the geographic North Pole). The declination is positive when the magnetic north is east of true north. The term magnetic variation is a synonym, and is more often used in navigation. Isogonic lines are where the declination has the same value, and the lines where the declination is zero are called agonic lines. The lowercase Greek letter δ (delta) is frequently used as the symbol for magnetic declination.
Somewhat more formally, Bowditch defines variation as “the angle between the magnetic and geographic meridians at any place, expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north. The angle between magnetic and grid meridians is called grid magnetic angle, grid variation, or grivation. Called magnetic variation when a distinction is needed to prevent possible ambiguity. Also called magnetic declination.”
A compass rose, sometimes called a windrose, is a figure on a compass, map, nautical chart or monument used to display the orientation of the cardinal directions—North, East, South and West—and their intermediate points. It is also the term for the graduated markings found on the traditional magnetic compass. Today, the idea of a compass rose is found on, or featured in, almost all navigation systems, including nautical charts, non-directional beacons (NDB), VHF omnidirectional range (VOR) systems, global-positioning systems (GPS), and similar equipment and devices.
Science of drugs including their origin, composition, pharmacokinetics,
pharmacodynamics, therapeutic use, and toxicology.
Pharmacology (from Greek φάρμακον, pharmakon, "poison" in classic Greek; "drug" in modern Greek; and -λογία, -logia "study of", "knowledge of") is the branch of medicine and biology concerned with the study of drug action, where a drug can be broadly defined as any man-made, natural, or endogenous (within the body) molecule which exerts a biochemical and/or physiological effect on the cell, tissue, organ, or organism. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function. If substances have medicinal properties, they are considered pharmaceuticals.