[anlb4]

Good Morning...Could you tell me what substitution and addition mean in organic chemistry..we are studying hydrocarbons and functional groups

[jdurg]

Substitution is as its name describes; a substitution of one component (I.E. functional group) for another.  Let's say you have the formula H₃C-CH₃ and you perform a substitution reaction involving an OH group.  The OH group will replace one of the H's in the molecule giving you an alcohol;  H₃C-CH₂OH.

An addition reaction is when a functional group or atom is added to a molecule.  so if you had H₂C=CH₂ and performed an addition reaction with fluorine, you'd get FH₂C-CH₂F.  So the fluorine gets added to the compound.

[dexangeles]

ditto above

but I believe substitution refers more to functional groups and not the entire compound

[jdurg]

ditto above

but I believe substitution refers more to functional groups and not the entire compound

Indeed.  Just a wrong choice of words on my part.