My youngest girl is 16 months old and she can only say like 5 things and I'm worried her sister could say a lot more things by now. How can I convice her to talk more.

Do you talk to her a lot?

Play learning games with her?

Kids learn at a different pace because every child is different. Your going have to be patient with her and work with her every day and you will see an improvement.

Also, if you have a concern you can voice it with her doctor but most doctors won't think it is an issue until the child is at least 24 months or older.

My mother told me that my brother starting walking at 11 months, I started a day before my 1st birthday and my sister didn't start until she was 13 months. Every child is different.

Do you find that your other daughter may answer for your youngest? A lot of times the 2nd child doesn't speak as much because the older siblings talk for them.
This happened with my brother. My mom was really worried that he couldn't speak. He is the youngest of 4 kids. What was actually happening is that we did all the talking for him.

You just need to be patient. Continue to talk to her and help her identify her surroundings. Your doctor will guide you if there is a problem.

Before I answer, I need to know how old her older sister is.