The purpose of transition words is to connect your sentences to make them flow. There are transition words for agreement, opposition, cause, and emphasis.
Agreement: In addition to, also, likewise, furthermore, additionally, as well as
Opposition: In contrast, although this may be true, on the contrary, instead
Condition: In the event that, granted (that), if, for the purpose of, so long as
Emphasis: In other words, to be sure, indeed, to put it differently, for this reason
