What is the logic of "proactive" and "cojoined"?  Has the prefex been
added to give greater emphasis to the word?

Hello psdir-ga,

It seems that the prefix in each case has a function beyond mere
emphasis.

Apparently "proactive", in the sense of "acting in anticipation of
future problems, needs, or changes", was formed on the model of
"reactive".  So, instead of acting in response to something
(re-acting), a person can act in anticipation of something
(pro-acting).

"proactive"
Merriam-Webster
http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=proactive

Meanwhile, "conjoin" (the more common version of the word sometimes
called "cojoin") means "to join together", and has been around for a
long time.  The words do seem to overlap, but not completely.  You can
join a club; you cannot "conjoin" it.  You could say that two objects
that have been fused into one larger object are "joined", but people
might understand you more quickly if you say "conjoined" (or "joined
together").

"cojoin"
Dictionary.com
http://dictionary.reference.com/search?q=cojoin&r=67

"conjoin"
Merriam-Webster
http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=conjoin

- justaskscott-ga


Search terms used on Google:

cojoin
site:m-w.com conjoin
site:m-w.com proactive