Fluency refers to the rate and rhythm of speech when talking. When a person has difficulty with fluency we often refer to that as stuttering or stammering. There are different types of stuttering behaviors that can be addressed in speech therapy and everyone is different!
It is important to know that everyone stutters at some point in their life, whether as a child learning a new skill or as an adult speaking in front of large crowds when it is fairly common to "trip over" our words. These are called typical dysfluencies which are whole word or phrase repetitions (i.e. "The dog..the dog.. the dog is running) or interjections (i.e. "I um will go to um the store later").
There are also those who find themselves stuttering more frequently and with more strain which are atypical dysfluencies . Atypical or Stuttering-like dysfluencies are single sound repetitions (i.e. "a..a...a...a dog is running"), part word repetitions (i.e. "a d..d..d..dog is running"), prolongations (i.e. "aaaa dog is running"), or a block (i.e. "........ a dog is running").
If you or your child exhibits stuttering behaviors you should seek the advice of a Speech Pathologist.