When a speech sound changes, and becomes more like another sound which follows it or precedes it, this is called assimilation. Assimilation is more likely to be found in rapid, casual speech and less likely in slow, careful speech. Speaker assimilate to avoid awkward combinations which lead to loss of oral fluency. Assimilation in terms of place of articulation is the most common. That is the final consonant(Cf) of the first word assimilates the place of articulation of the initial consonant(Ci) of the second.