Definition:Nadir

Definition

Consider the celestial sphere $C$ with an observer $O$ at the center.

Let $Z$ be the zenith of $C$

Let the straight line $ZO$ be produced from $O$ to meet $C$ at $R$.

The point $R$ is known as the nadir of $C$.

In the above diagram, the nadir is indicated by $R$.

Also see

• Definition:Zenith

Linguistic Note

The word nadir derives from the Arabic نظير‎ (naẓīr), meaning counterpart.

It is usually pronounced nad-deer or nay-deer, although the stress can sometimes be heard on the second syllable: nad-deer.

Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): celestial sphere
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): nadir
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): celestial sphere
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): nadir