As a "part of speech" transition words are used to link words, phrases or sentences. They help the reader to progress from one idea (expressed by the author) to the next idea. Thus, they help to build up coherent relationships within the text.
This structured list of commonly used English transition words — approximately 200, can be considered as quasi complete. It can be used (by students and teachers alike) to find the right expression. English transition words are essential, since they not only connect ideas, but also can introduce a certain shift, contrast or opposition, emphasis or agreement, purpose, result or conclusion, etc. in the line of argument.
The transition words and phrases have been assigned only once to somewhat artificial categories, although some words belong to more than one category.
There is some overlapping with prepositions and postpositions, but for the purpose of usage and completeness of this concise guide, I did not differentiate.
The transition words like also, in addition, and, likewise, add information, reinforce ideas, and express agreement with preceding material.
in the first place
not only . but also
as a matter of fact
in the same fashion / way