They add or concede a point, indicate placement in time or location, signal more or new information, and announce the impending conclusion.
In a discussion of whether scientific genius is constant, Robert Weisberg¹ identifies a common misconception of genius:
One characteristic believed to be associated with scientific genius is a greater sensitivity to potentially solvable problems.
He then uses transitions to guide the reader through his thinking while building to his most important point:
The last section raised doubts about… One example of such misdirection… Another example of misdirected scientific genius is seen… Still another example… A similar case is that of… Perhaps the most striking example of a scientific genius making the wrong choice… The most important point… In summary…
When Weisberg is ready to shift topics away from the discussion of “greater sensitivity,” he uses an entire sentence as a transition:
These examples can also be used to disprove another intuition concerning genius: even the greatest scientists are not uniformly creative throughout their lives.
This transitional sentence includes (1) a lump summary of the the three previous pages (“these examples”), (2) a shift in focus (“can be used to disprove”), and (3) the topic of the next discussion (“even the greatest scientists are not uniformly creative throughout their lives”). Once the “not uniformly creative” discussion is underway, he returns to using transition phrases, such as “on the contrary” and “it is also true, however” and “in addition” to link each new point to the one before.
¹ Weisberg, Robert W. Creativity: Genius and Other Myths. What You, Mozart, Einstein, & Picasso Have in Common. W. H. Freeman and Company, New York. 1986. Print.