### Isolines

Isolines are often used on maps to represent points of equal value. This is a list of some common (as well as obscure) types of isolines. The prefix "iso-" means "equal."

- A line representing points of equal atmospheric pressure

**isobar**

- A line representing points of equal depth under water

**isobath**

- A line representing depths of water with equal temperature

**isobathytherm**

- A line representing points of equal recurrence of auroras

**isochasm**

- A line representing points of equal mean winter temperature

**isocheim**

- A line representing points of equal time-distance from a point, such as the transportation time from a particular point

**isochrone**

- A line representing points of equal transport costs for products from production to markets

**isodapane**

- A line representing points of equal intensity of radiation

**isodose**

- A line representing points of equal dew point

**isodrosotherm**

- A line representing points of equal mean temperature

**isogeotherm**

- A line separating linguistic features

**isogloss**

- A line representing points of equal magnetic declination

**isogonal**

- A line representing points of equal salinity in the ocean

**isohaline**

- A line representing points receiving equal amounts of sunshine

**isohel**

- A line representing points of equal humidity

**isohume**

- A line representing points of equal precipitation

**isohyet**

- A line representing points of equal amounts of cloud cover

**isoneph**

- A line representing points where ice begins to form at the same time each fall or winter

**isopectic**

- A line representing points where biological events occur at the same time, such as crops flowering

**isophene**

- A line representing points of equal acidity, as in acid precipitation

**isoplat**

- A line representing points of equal numerical value, such as population

**isopleth**

- A line representing points of equal annual change in magnetic declination

**isopor**

- A line representing points of equal atmospheric density

**isostere**

- A line representing points where ice begins to melt at the same time each spring

**isotac**

- A line representing points of equal wind speed

**isotach**

- A line representing points of equal mean summer temperature

**isothere**

- A line representing points of equal temperature

**isotherm**

- A line representing points of equal transport costs from the source of a raw material

**isotim**