The correct order of basic strength in aqueous solution is:
In aqueous solution, secondary amines like (CH₃)₂NH are stronger bases than primary (CH₃NH₂) and ammonia (NH₃) due to solvation and inductive effects, as per the PDF.
Ref: NCERT Class 12 Chemistry > Chapter 13: Amines > Topic: Chemical Reactions - Carbylamine Reaction and General Reactions