其实如果用英语解释区别就很明确了：
pressure:the action of putting force or weight onto sth.
eg:The pressure of the water turns this wheel,and this is used
to make electric power.
stress:(a state of wory resulting from)pressure caused by the
problems of living,too much work,etc.
eg:He's under a lot of stress because his wife is very ill.
strain:the condition of being tightly pulled or streched
eg:The rope broke under the strain.
burden:sth. that is carried;a load
eg:a heavy burden