In a rhombus, adjacent sides are equal (it means all sides are equal. Right???) Then instead of saying that "in a rhombus all sides are equal", we say that "in a rhombus adjacent sides are equal". Why????

The definition of rhombus has been defined in such a way that  If adjacent sides of a parallelogram are equal, then the parallelogram is a rhombus. We say that all sides of rhombus are congruent i.e equal in length . One or other way of saying which means almost same .