A "ken" is not a widely recognized unit of measurement in modern systems. However, the term "ken" is more commonly used as a noun or verb in English and has a different meaning.
As a noun, "ken" refers to one's range of sight, perception, or understanding. For example, you might say, "Beyond my ken," to mean something is beyond your understanding or knowledge.
As a verb, "ken" means to understand, perceive, or know. For instance, you might use it in a sentence like, "I cannot ken the complexity of this issue."
In these contexts, "ken" is used to describe one's ability to perceive or comprehend something, rather than a unit of measurement. If you have a specific context in which "ken" is being used as a unit of measurement, please provide more details, and I'll do my best to assist you further.
A "span" is a traditional unit of length used for measuring cloth or fabric. It was historically used in various countries, including England, and is based on the width of the human hand or the spread of the fingers. The actual length of a span could vary depending on the region and historical context.
In England, a span was typically equal to 9 inches or approximately 22.86 centimeters. However, it's important to note that the definition of a span could vary from place to place and over time.