<p>What do they mean, how do you use them in what context?</p>
<p>Also, are there any other words like this that start with WHERE-?</p>
<p>whereas means “while (on the other hand)”: “I like cake whereas he hates cake.”
whereby means “by which” or “through which”: “I devised a method whereby energy is perpetual and lasts forever.” The implication is that energy is perpetual through the method, i.e., when you employ the method, you get energy that’s perpetual.
wherein basically means “where” (or “in which”): “There is a house wherein people live.” The implication is that people live in the house.</p>
<p>These definitions (and example sentences) can be accessed through any dictionary, perhaps on the internet. On the internet there are dictionaries whereby you can see the definitions of words. Dictionaries, wherein virtually all words in the English language are defined, are helpful: Using a dictionary is efficient whereas asking for definitions of words on an online forum is less efficient.</p>
<p>“Whereas” can also be used in a formal sense as the start of a resolution (often from a legislature). Legislative proclamations honoring someone often start out with “whereas.” For example: “Whereas John Biddlemeister has served as the Mayor of the Village of Frankenhuysermeerstein for the past 37 years, we the Legislature of the State of X grant $3700 for the purpose of constructing the Biddlemeister monument in the Village.”</p>