Possible cause is Normal period of nonfluency. Action to take Your child is learning to coordinate his thoughts with his motor skills. Speak clearly and read to your child. Don't overcorrect him or finish his sentences. This stage usually passes quickly.
Possible cause is Normal development.
Action to take Many children don't master consonants until age 5. Possible cause is Lisp or other speech impediment. Action to take If the impediment is marked, ask your pediatrician to recommend a speech therapist for an evaluation. Possible cause is Stammering or stuttering. Action to take Consult your pediatrician who may recommend an evaluation by a speech therapist.