declination

In astronomy, the declination of a celestial object (such as a star or planet) is its position in relation to the celestial equator—the imaginary flat surface that extends out from Earth’s equator in all directions.

In astronomy, heavenly bodies like planets and stars are considered in terms of their position in the celestial sphere—the imaginary sphere that extends out infinitely from Earth. (Picture an infinitely huge ball with Earth as its center.) The celestial equator cuts this sphere in half.

Declination involves the measurement of the position of such objects as being north or south of the celestial equator. Those north of the celestial equator are measured in positive degrees, and those south of it are measured in negative degrees. The declination of the north celestial pole is 90° and the declination of the south celestial pole is -90°. For example, during the summer solstice in the Northern Hemisphere, the Sun is at a declination of 23° north.

Declination also has several more general meanings, but none of them are commonly used. In most of these cases, there is another, more common word that can be used in its place.

Declination can mean a bending or sloping downward. Things that slope this way, such as the parts of a plant, can be described with the adjective declinate. Declination can also mean deterioration—the process or an instance of something getting worse. In both of these senses, it can often be replaced with the noun decline. Declination can also refer to deviation, such as from a standard.

A declination can also be a polite refusal, especially in a formal or official situation. In this sense, it is a noun form of the verb decline, meaning to refuse or to turn something down.

In most cases, it’s much more common for people to use words like deterioration, decline, deviation, and refusal than declination.

The first records of the word declination come from the 1300s. It derives from the Latin dēclīnātus, meaning “turned aside.” Both decline and declination ultimately come from the Latin verb dēclīnāre, meaning “to slope” or “to bend away.”

Because space is three-dimensional, it’s often considered in terms of spheres, curves, and slopes, as opposed to straight lines. In astronomy, the declination of an object like a star is kind of like its latitude and longitude. But instead of being measured on the sphere of Earth, it’s measured on the celestial sphere—the imaginary sphere of space.

What are some other forms related to declination?

• declinational (adjective)
• predeclination (noun)

What are some synonyms for declination?

• decline
• deterioration
• deviation
• refusal

What are some words that share a root or word element with declination? 

• decline
• declinate 
• declinatory

What are some words that often get used in discussing declination?

• celestial equator
• celestial sphere
• celestial pole
• position
• degree
• measurement
• astronomy

The term declination is mostly used in astronomy. Its more general senses are rarely used.

It will reach its highest declination on Saturday but highest elevation later in the month. A subtle but important difference.

— David Blanchflower (@DavidBflower) July 15, 2020

I looked up the approximate departure declination for those dates in the Interplanetary Mission Design Handbook, then I have a spreadsheet for computing (among other things) launch azimuth from the desired injection orbit. pic.twitter.com/KpeDqeWRWh

— Max Fagin 🚀🔴🌐☄🌘 (@MaxFagin) July 8, 2020

The winter solstice happens every year when the Sun reaches its most southerly declination of -23.4 degrees. In other words, it is when the North Pole is tilted farthest away from the Sun, delivering the fewest hours of sunlight of the year. pic.twitter.com/wQr101iabM

— A to Z of Paganism (@asolitarypagan) December 9, 2019

Which of the following words is a synonym of declination?

A. decline
B. deterioration
C. deviation
D. all of the above