according to Cambridge Dictionary: constrain /kənstreɪn/ verb [ T often passive ] = to control and limit something . ex: The country's progress was constrained by a leader who refused to look forward. restrain /rɪstreɪn/ verb [ T ] = to control the actions or behaviour of someone by force, especially in order to stop them from doing something, or to limit the growth or force of something ex: When he started fighting, it took four police officers to restrain him. [ R ] She was so angry that she could hardly restrain her self . You should try to restrain your ambitions and be more realistic. Growth in car ownership could be restrained by increasing taxes.

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