I wouldn't be "worried" necessarily, but this may be a cause for concern. All children develop language at varying rates, and I am sure that your daughter is well within her developmental norm. However, there are a few things for you to consider. Have you had her hearing checked? Have you spoken to your pediatrician about having her evaluated for early intervention? It is possible that she may have a speech delay, especially since her speech isn't progressing over time. How is her receptive language? Does she understand everything you tell her, and follow 1 to 2 step commands? A child at 14-15 months old is expected to speak at least two words skillfully.... At 15 months, my son was saying approximately 10 words and was already putting words together, such as "Hey Daddy." He's always been advanced linguistically, so that is no means for comparison - I just want you to know what some children her age are capable of. I recommend reading to her frequently, and having environmental print around your home (such as her name spelled on signs, pictures labeled with words that you read together, etc). She may have a language explosion in a few months... I would give it some time - but if she isn't speaking more by her 18 month well child checkup, I would definitely pursue this further. Best of luck!