Repetition of movements, act, words and phrases; beyond the point of relevance -
Perseveration:- repetition of words, or motor activity beyond the point of relevance. You should keep in mind that in perseveration, there may be a repetition of speech (words, phrases) or motor activity (movement) or both.
Stereotype: -A continuous mechanical repetition of speech or physical activity which is not goal oriented and occurs in the absence of any external stimulus.
Now, you must be thinking that both perseveration and stereotypy are a repetitive motor activity or speech, Then what is the difference between them ? Read below -


Perseveration is goal-directed (However, it is repeated beyond the fulfillment of goal), on the other hand, stereotypy is not goal-directed.
Perseveration requires an external stimulus, but stereotypy does not.


For example:-


If you ask the person `QI - What is your name?' Ansi- Ramesh'. Q2 - 'Where are you'. Ans2 - 'Ramesh'. Q3 ­'What is the Day'. Ans 3 - 'Ramesh'. This is an example of perseveration. Here the external stimulus is given by asking the Question and the person gave a goal-directed answer. However, he repeated the same answer again, i.e. repetition beyond the fulfillment of a goal.
In stereotypy, a person continuously repeats speech eg. by saying 'you are old & sick', 'you are old & sick', 'you are old & sick', without any external stimulus. The speech is not goal-directed.
Fusion
Mannerism
Perseveration
Stereotypy