Recently I have met a number of nouns with suffixes -er,-ar etc.I didn't know that they
are derivative nouns.
,e.g.planet,sugar,basket,cement,instrument and so on.IT was given in USEFUL ENGLISH
I DOUBT WHETHER IT IS correct or not.
But I didn,t come across the suffix -ire as in millionaire.Is it a derivative word?
No, the examples you cite are not derivatives since their endings are not actually suffixes.
"Millionaire" has the suffix -aire found in loanwords from French and which is used to denote someone who has a million pounds or dollars: "million + -aire"
Other examples of loanwords from French include: "concessionaire", "doctrinaire", "commissionaire" "and "legionnaire".