Similar to ammonia, primary & secondary amines have protic hydrogens and thus they showcase a degree of acidity. Whereas tertiary amines have no protic hydrogen and thus do not possess a degree of acidity.
pKa value for primary & secondary amines is about 38, which makes them a real weak acid. Whereas if we take the pKb, it is about 4. This makes the amines much more basic than acidic. Thus, an aqueous solution of an amine is strongly alkaline.