Scalene Triangle
A triangle is the polygon bounded by least number of sides. As you all know a triangle has exactly three sides. Triangles are classified according to the angle measures or according to side lengths.
The classification done on the basis of number of congruent sides are as follows:
Scalene Triangle  In this type of triangle, the two sides are never congruent.
Isosceles Triangle  In this type of triangle, a minimum of two sides are congruent.
Equilateral Triangle  In this type of triangle, all the 3 sides are congruent.
Scalene triangles not only have distinct side lengths, but also distinct angle measures. The classification of Scalene triangles can be further refined considering the angle measures as well as, acute scalene, obtuse scalene and right scalene triangles.

 
Scalene Acute Triangle: Has three sides are of different lengths and all the three angles are acute. 
Scalene Obtuse Triangle: Has three sides are of different lengths and one obtuse angle at P.  Scalene Right Triangle: Has three sides are of different lengths and one Right angle at R. 
Scalene triangle is taken to be the default triangle, if no additional information is given.