in the digstive system,what is the defenition or function of th Appendix?

Are we talking about the human appendix? Other animals also have an appendix.

See here for brief descriptions

http://dictionary.reference.com/browse/appendix

You might also want to look at

http://www.scientificamerican.com/article.cfm?id=does-the-appendix-serve-a

how do animals need enviroment

The appendix is a small, finger-shaped pouch located at the beginning of the large intestine, on the right side of the abdomen. While the exact function of the appendix is still somewhat debated, it is generally considered to be a vestigial organ, meaning it no longer serves a significant purpose in humans.

Throughout evolution, the appendix likely played a role in aiding digestion in our ancestors. It may have helped break down tough plant fibers or acted as a reservoir for beneficial gut bacteria. However, as human diets and lifestyles have changed over time, the appendix has become less important.

In some cases, the appendix can become inflamed or infected, leading to a condition called appendicitis. This can result in severe abdominal pain and may require surgical removal of the appendix. While the appendix itself is not essential to survival, if left untreated, appendicitis can be life-threatening.

To learn more about this topic or any other question you may have, you can perform a simple Google search using keywords such as "function of the appendix" or "appendix anatomy and purpose." This will provide you with various reliable sources explaining the topic in more detail.