形容詞形式：
以-n結尾的國家后面一般加-ese,【如中國和日本】；
多數(shù)西方國家后面加-n【如俄羅斯和美國】；
極少數(shù)國家是特殊形式【如法國France--French】.
至于人口,單數(shù)基本等于上述變法；
對于復數(shù),則有【中日不變英法變,其他后邊加-s】的說法：
這個表格應該能幫你解決難題.
┏國家┳┳┳┳┳┳┳┳人口單數(shù)┳┳┳┳┳┳┳┳復數(shù)┳┳┳┳┳┳┳┳┳┓
┣China╋╋╋╋╋╋╋╋Chinese╋╋╋╋╋╋╋╋Chinese ╋╋╋╋╋╋╋┫
┣Japan╋╋╋╋╋╋╋╋Japanese╋╋╋╋╋╋╋ Japanese╋╋╋╋╋╋╋┫
┣╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋┫
┣England╋╋╋╋╋╋╋Englishman╋╋╋╋╋╋╋Englishmen ╋╋╋╋╋┫
┣France╋╋╋╋╋╋╋ Frenchman╋╋╋╋╋╋╋╋Frenchmen ╋╋╋╋╋┫
┣╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋╋┫
┣America╋╋╋╋╋╋╋American╋╋╋╋╋╋╋╋╋Americans（注意-s）┫
┣Russia╋╋╋╋╋╋╋ Russian╋╋╋╋╋╋╋╋╋ Russians ╋╋╋╋╋┫
┗…┻┻┻┻┻┻┻┻┻…┻┻┻┻┻┻┻┻┻┻┻…┻┻┻┻┻┻┻┻┻┻┛
————————明白了吧,我可累慘了@^@————————