Periodisation is coined from the word period. Periodisation in history simply means the historian attempt to split the wide history of man and societies into smaller and district periods to make it a lot easier and interesting to study. It would be impossible to appreciate the whole history of a nation over thousands of years at a stretch. Hence, periodisation is used to carefully set aside a particular period or time frame in the history of any society to be studied. For example, we often periodise the study of African history as Africa from the earliest time to 1500A.D, Africa from 1500 to 1800A.D. or Africa in the 19th and 20th centuries.
However, it is important to note that in periodisation, care is taken so that it is not done carelessly. Most times in history, we look out for epochs or events that mark turning points or very significant periods in the history of any society when attempting to periodise. For example, in Nigerian history, significant events like the pre-colonial era, and the post-colonial era i.e. colonial era, and the period from independence are used. In all cases, the historian must state why the period chosen is considered significant.
Again, care must be taken so that it does not appear as if the process of history is being rigidly broken, because history as a process of unwinding of events cannot be easily broken. Periodisation is only an attempt to study certain selected period at a stretch. We also pay attention to the importance of chronology and sequence in order not to distort or disjoint history.