Some words that end in "ies" are babies, puppies, and hobbies.
pies
spies ponies armies bullies babies
Many of them change to -ies for the plural.
Some plural nouns that end in -es or -ies are:baby, babiesberry, berriesbox, boxesbranch, branchesflash, flashesfox, foxesglass, glassesguess, guesseskiss, kissesmatch, matchesmiss, missespony, poniesquiz, quizzesshelf, shelvesstory, storieswaltz, waltzeswatch, watcheswish, wisheswolf, wolveswrench, wrenches
Vicinities, almost all plurals of words that end "y" is "ies".
Words that drop the ending "y" and add "-ies" are those for which the penultimate letter of the word is a consonant. As the penultimate letter of keys is a vowel, the final consonant y is retained and an s is added at the end.
When forming the plural of singular words that end in the letter Y, the Y is removed and replaced by IE, followed by the S. Examples : property / properties -- city / cities -- viscosity / viscosities
Some words that end in the vowel y and add es to form the plural are alley, journey, and key.
If the word has a consonant before the final 'y' then the plural ends with 'ies':baby - babiespuppy - puppiesbully - bullieslily - liliesIf the word has a vowel before the final y then you just add an 's':day - daysmonkey - monkeystoy - toyssurvey - surveys
The suffix in the word duties is -ies. This suffix just makes words plural.
Some examples of nouns that the plural form ends with -ies are:try, triesfry, friessupply, suppliesparty, partiespanty, pantiespatty, pattieslady, ladiesbaby, babiesworry, worriescherry, cherries