What is the definition of "oikos," a root in the word "ecology?"
One method of understanding the meaning of a new word is to dissect the word into is components- prefixes (beginning parts of words), root words (oftentimes from the ancient Greek or Latin languages) and suffixes (ending to words). If one becomes familiar with the meaning of such word parts, then he/she can create definitions to new words as they arise. Links to lists of such word components are provided below.
Oikos is the Greek root for "the whole house" and is used in relationships to the household, house, or family. The word implies a set of interdependent components that, collectively, form an integrated whole. For example, "ecology" (as mentioned within your question) is a system whose elements (flora, terrain, and organisms) interact with the environment.