A line joining places having an equal degree of cloudiness is an

A line joining places having an equal degree of cloudiness is called an isoneph.

To understand this better, let's break down some related terms:

• Isotherm: These are lines on a map that connect points having the same temperature at a given time or on average over a given period.
• Isohyet: These are lines that connect areas receiving equal amounts of precipitation, such as rainfall.
• Isoneph: These are lines that link points experiencing the same degree of cloud cover or cloudiness.
• Isobar: These are lines on a weather map that connect points of equal atmospheric pressure.

So, when we are specifically talking about cloudiness, the correct term and line is an isoneph. This is useful in meteorology for visualizing and analyzing patterns of cloud coverage across different regions.