Defining your terms
It is very important in an paper to define key terms so that
A. you show you understand them, and
B. you let your reader know how you are using them.
C. you alert your reader that terms may be problematic, ambiguous, or subject to change over time (or within particular contexts).
A good place to define key terms in an paper is in the introduction or the opening paragraphs in the main body. Consider the two examples below:
"First, many factors converge to make poverty a complex, multidimensional phenomenon. Second, as expected, poverty is routinely defined as the lack of what is necessary for material well-being — especially food but also housing, land, and other assets. Poverty is the lack of multiple resources leading to physical deprivation. Third, poor people’s definitions reveal important psychological aspects of poverty. Poor people are acutely aware of their lack of voice, power, and independence, which subject them to exploitation. Their poverty also leaves them vulnerable to rudeness, humiliation, and inhumane treatment by both private and public agents of the state from whom they seek help. Poor people also speak about the pain brought about by their unavoidable violation of social norms and their inability to maintain cultural identity through participating in traditions, festivals, and rituals. Their inability to fully participate in community life leads to a breakdown of social relations. Fourth, the absence of basic infrastructure — particularly roads, transport, water, and health facilities — emerged as critical. While literacy is viewed as important, schooling receives mixed reviews, occasionally highly valued but often notably irrelevant in the lives of poor people. Finally, poor people focus on assets rather than income and link their lack of physical, human, social, and environmental assets to their vulnerability and exposure to risk."
From: Narayan et al. Can Anyone Hear Us? Voices from 47 Countries, World Bank Publication, December 1990
The writer, in this instance, has explained the complexity of the definition of poverty. The writer has guided the reader through a series of different areas which are important in the consideration of the what poverty. The list of different factors which relate to poverty and make up the definition, in fact go on to make up separate sub-chapter headings in this chapter which is titled "Poverty Definitions". Clearly therefore definition is extremely important to this writer. Indeed it should be important to all NAPC staff as well, because accurate definitions help the reader to understand exactly what you mean.
The implications on poverty in the developing world of biofuels - renewable energy produced from organic matter by converting the complex carbohydrates in organic matter into energy - are significant. The potential is large, whether through employment, wider growth multipliers and energy price effects. But it is also fragile: it will be reduced where feedstock production tends to be large scale, or causes pressure on land access, and its success can be undermined by many of the same policy, regulatory or investment shortcomings as impede agriculture.
From Peskett et al. Biofuels, Agriculture and Poverty Reduction, in Natural Resources Perspectives, ODI, June 2007
The writer in this example first qualifies what he means by reference to biofuels, by using the dashes to allow for further explanation (thus allowing the reader to follow her train of thought). He then goes on to discuss how the potential benefits but also the potential harm that could be caused by biofuel development, giving the subject nuance and depth from the beginning.
Where can you find reliable definitions of words?
Using a reputable dictionary or encyclopedia should be a first port of call. Also considering using other academic material to find a definition.