Please check my answer thank you.

Gastrectomy is listed as the principal procedure on the surgical report. You know that (-ectomy) means excision or surgical removal. What part of the medical word does "ectomy " represent ?

A. Root
B. Suffix
C. Prefix
D. Combining form

My answer is Suffix (b)

Is it suffix or combining form? My first thought was to agree with you that it's a suffix. However, this site would indicate it's a combining form.

http://www.thefreedictionary.com/combining+form

Your answer is correct. "ectomy" is a suffix in the medical word "gastrectomy." A suffix is a word part that is added at the end of a root word to modify its meaning. In this case, "ectomy" indicates the surgical removal or excision of the stomach. Well done!