Functional groups vs. Substituents

[Nataliya Karashchuk]

What is the difference between a functional group and a substituent? Would carboxylic be considered just a functional group or would it also be a substituent?

[Tara Kubilay 2A]

Substituent are essentially Hydrocarbon chains that are shorter than and connected to the parent chain. (They are missing one H where the fist Carbon is bound to the parent chain and they therefore are actually called Hydrocarbyls). Hydrocarbons, by definition, consist of Hydrogen and Carbon atoms that are connected through single bonds. This simple definition should help distinguish between substituents and functional groups. Carboxylic Acid -COOH has oxygens and a double bond and is a functional group, not a substituent.

Another important point is that functional groups have certain characteristics that determine how they react with other molecules.

[Stevie Wisz]

So, basically, the difference is that functional groups may contain atoms other than C and H like N or O while substituents are only hydrocarbons?