In order to indicate how different parts relate to each other, you can use transition words such as “because,” “however,” and “similarly.” In that way, you signal how your reader should read your text. You indicate, in short, what you want to communicate.
Imagine that you present the results of two different studies. You clearly need to account for the results of each study, but you should also indicate how they relate to each other – otherwise you risk merely listing results, as in the following sentence. “Smith et al. report that 76 % of the participants experienced that daily exercise relieves pain. In Jones et al., 84 % of the participants stated that daily exercise relieved pain”. Not very smooth, right?
If you instead link the two results and indicate how they relate to each other, the text not only becomes easier to read, but it also more meaningful. “Smith et al. report that 76 % of the participants experienced that daily exercise relieves pain. Similarly, 84 % of the participants in Jones et al. reported this effect.” The similarity is indicated with a transition word (“similarly”) and strengthened with a pronoun which keeps the text together (“this”).
If you instead have two results that are very different, you may highlight the difference with a transition word that indicates contrast, for example ”however.” “Smith et al. report that 76 % of the participants experienced that daily exercise relieves pain. However, no such connection was found in Johansson et al. (the word “such” helps keeping the text together).
If you do not indicate how different parts of your text relate to each other, your text becomes less communicative. There is a risk that your reader fails to see how different parts relate to each other, or that it takes them longer to see these links (remember that the links you want to highlight are often much less obvious than the ones in the example). There is also a risk that your reader sees these links, but is unsure if you see them too or if you are, perhaps, merely listing results. That scenario would of course be especially unfortunate when you write a text for academic credit, since your reader/teacher needs to make sure that you have understood the material you present.
However, sometimes it may be difficult to find the right transition words. That may be because you have not yet decided how the different parts relate to each other – and you will then have to consider this carefully. When you are carefully contemplating the transition words you use, you also have to consider your material and what you really want to communicate. Transition words are, in other words, useful both to your reader and to yourself.