Wereside is a synonym for the word "therioside". The two terms have the same definition and may be used interchangeably.
The therioside is the aspect of a therianthrope (aka a therian, or were) that they feel is a nonhuman animal.
It is synonymous with the term "wereside", and is used in exactly the same way. It is related to the term "theriotype."
You may, for example, hear a therian say "I have a fox wereside" or "I have a fox therioside" to indicate that they are a fox therian.
Some therians speak of their theriosides as almost being seperate from the rest of their personality, while others merely use the term therioside to indicate certain aspects of their outlook, reactions, or perceptions that they don't feel stem from their human nature.
You will occasionally hear of a Mental Shift as being "when someone's therioside is in control", or "in the foreground".
Weres will occasionaly speak of their therioside as being easier or harder to get in touch with, based on circumstances, mood, life events, etc.
Many weres claim that when they must interact strongly with "the human world", jobs, school, etc. that their "human side" is more close to the foreground, and the "animal side" takes a backseat, or is more difficult to feel.
At other times, perhaps when very happy, or sad, or excited, or even when endangered, they may "feel their therioside" more strongly.