Practical English Usage   (Michael Swan)

about and on

compare :

-        a book for children about Africa and peoples. 

-       a text book on African history.

-        a conversation about money.  

-        a lecture on economics.

   We use "about" to talk about ordinary, more general kinds of communication.

 "on" suggests that a book, lecture, talk etc. is serious or academic, suitable for specialists.

( from mis.bitarafan )

Word Formation   (John Sinclair)

 Making new words by adapting old ones is very popular at present.

 By learning suffix and prefix you can gain this goal. 

a_: occurs in words which have 'not', 'without', 'opposite to' as part of their meaning.

         for example someone who is 'amoral'  has no moral standards or principles . Here

         is some words with this meaning :

 apolitical: (adj) having no interest or involvement in political affairs.

 eg. a group of apolitical young professional people. 

asexual: (adj)  not having sexual organs or not involving sex.

 eg. Alpine flowers are often among the most asexual of flowers.

 asocial: (adj) rejecting or lacking the capacity for social interaction.

 eg . Every body knows him an asocial person.

 atypical: (adj) not typical or usual.

 eg. This bird is atypical of most species here in that it does not build a nest.

 aformal, amoral, asensual, ...

( from mis.bitarafan )