Stammering is an interrupted way of speaking, blocking of speech or repetition of the same letter or word. If the normal flow of speech is hampered in any way, it is called stammering. There is a wrong belief amongst a section of the people that stammering means severe speech problem, but in reality, stammering may be minor, medium or severe.There is no difference between stammering and stuttering. Stammering is commonly used in UK and India. Stuttering is the term used in US and some other countries. Incorrect pronunciation of sounds or words is not stammering, it is called lisping.
Stammering may be in the form of mind block, hesitation, blocking, taking more time to utter any word, repeating any particular starting sound or the word itself, elongating words more than normal and forceful sound due to unnecessary excessive exhalation. It is an in-coordination among respiratory, vocal cords and articulatory mechanisms. Stammering is speech which is hesitant, stumbling, tense or jerky to the extent that it causes anxiety to the speaker.
The good news is that stammering is not a disease. There is nothing wrong with the tongue, throat or any other speech organs. When you speak alone or sing, you do not stammer. Sometimes you can talk very fluently. It means that it is purely a bad habitual and psychological problem and any bad habit can be keyword 100% cured with a right approach to tackle the problem.