What is the different between primary amine and secandary amine?

primary amine has one R group

secondary amine has two R groups 

we get Primary amines when one of3 hydrogen atoms in ammonia is replaced by an organic substituent.but for Secondary amines have2 organic substituent to the N atom and one H

Amines are organic derivatives of ammonia, in which one, two, or all three of the hydrogens of ammonia are replaced by organic groups. Compounds RNH­2 are called primary amines, R2NH secondary amines, and R3N are tertiary amines. The designation of amines as primary, secondary, and tertiary is different from the usage of these terms in connection with alcohols and alkyl halides.

Consequently, tertiary butylamine is a primary amine, but tertiary butyl alcohol is classed as a tertiary alcohol. Similarly, dipropylamine is a secondary amine, even though the R groups attached to nitrogen are primary.

Primary amine is related to only one radical ( ex:R-NH2) 

secondary amine is related to two radicals