Definition:Conchoid/Focus Point

Definition

Let $\KK$ be a conchoid.

Let $P$ be the fixed point on which the moving straight line $\LL$ is constrained to lie.

$P$ is known as the focus point of $\KK$.

Also known as

The focus point of a conchoid is also known as its pole.

Also see

• Results about conchoids can be found here.

Linguistic Note

The word conchoid derives from the Latin concha, which means mussel.

Ultimately the word derives from the Ancient Greek κόγχη (kónkhē) plus -oid, or directly from Ancient Greek κογχοειδής (konkhoeidḗs), which refers to anything with the general shape of a mussel shell.

It is properly pronounced kon-khoid, where the kh sound is the one found in the Scots loch or German ich.

However, it is commonplace to use the pronunciation kon-koid.

Note that the pronunciations kon-tshoid and kon-shoid are technically incorrect.

Sources

• Weisstein, Eric W. "Conchoid." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Conchoid.html