Definition:Conchoid/Directrix

Definition

Let $\KK$ be a conchoid.

Let $\CC$ be the curve with respect to which the conchoid is constructed.

$\CC$ is known as the directrix of $\KK$.

Also known as

The directrix of a conchoid is also known as its reference curve.

Also see

• Results about conchoids can be found here.

Linguistic Note on Directrix

The plural of directrix is directrices.

Linguistic Note on Conchoid

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.