hi hi1need, it varies from kid to kid.. mostly by 15 months, a toddler should be able to say mom, dad and 2-3 other words (eg: ball, cat, no etc..) but there is no thumb rule for this..
By 18 months toddlers need to have spoken atleast 6 words other than mama/papa. It can be in any language. There is no need for kids to speak these words continuously. Even if they have said it once it is ok. This is what my paed told me for my 20 month old. Now DD has start speaking more words.
i think max that a 15month old will use are 8-10 words. Though my son was a late starter he used to hardly utter 2-3 words. Later the paed told me that boys end up talking late compared to girls.infact the more you stress the boys to speak the more they will try to resist.I was relieved to say the least. So i think vocabulary of the kid depends on gender,people around the kid (like if they have grand parents,siblings etc around them then they start speaking early and have a better vocabulary)
My daughter is 15 months old she speaks few words Amma Anna Thatha Baby Daa for dog Flower She knows animal sounds Snake - hiss hiss, Horse - Neigh neigh , Sheep - Baa baa Hi, Hello , No ( uses frequently ), Tata....Papa....
As Nivimum said , I used to show my kid rhymes and he used to make all sounds like made by sheep, snake , cow etc... Also said basic words like amma , nanna, tata ,atta , bye etc.... Anyways dont worry it differs from kid to kid....
My 14 month says: mommom (for mommy) papa doggie sounds like ruff for dog, baba for sheep, kav kav for crow