Writing Your Thesis
What is a thesis?
The extended quote below is from pages 3 and 4 of "How To Write a Thesis" -- I like this definition! Especially since I agree that the undergraduate thesis is rather like a junior dissertation: it's all the same parts, but shorter and with a lighter "touch" in terms of expectations; in other words, "The differences between the undergraduate and postgraduate theses is one of degree rather than kind" (pg 3).
thesis/"Ti:sIs/ n 1 a proposition to be maintained or proved. 2 a dissertation esp. by a candidate for a degree. [Middle English via Late Latin from Greek = putting, placing, a proposition, etc.] 
a proposition made as a basis for reasoning without the assumption of
its truth. 2 a supposition made as a starting point for further
investigation from known facts. [Late Latin from Greek hypothesis
‘foundation’; Greek hypo ‘under’] 
might infer from the etymology above that a thesis is an
(obligatory) offering placed at the desk of the examiner by a candidate
who wishes to get a degree. This is the most common, and often only,
reason why a thesis is written. But there are other reasons for writing
A thesis is a written record of the work that has been undertaken by a candidate. It constitutes objective evidence of the author’s knowledge and capabilities in the field of interest and is therefore a fair means to gauge them. Although thesis writing may be viewed as an unpleasant obligation on the road to a degree, the discipline it induces may have lifelong benefits.
Most of all, a thesis is an attempt to communicate. Science begins with curiosity, follows on with experiment and analysis, and leads to findings which are then shared with the larger community of scientists and perhaps even the public. The thesis is therefore not merely a record of technical work, but is also an attempt to communicate it to a larger audience.
...In short, a thesis—whether undergraduate or postgraduate—is evidence of the candidate’s capacity to carry out independent research under the guidance of a supervisor,and to analyse and communicate the significant results of that work.NEXT