Based on Rome III criteria, functional disorders of GI are listed below: 
 Infant regurgitation:
-regurgitation two or more times per day for 3 or more weeks
-no retching, hematemesis, aspiration, apnea, FTT, abnormal posturing
Infant rumination syndrome:
-repetitive contraction of abdominal muscle
-regurgitation of gastric content in to the mouth and reswallowed
Cyclic vomiting syndrome:
-Two or more periods of intense nausea and vomiting lasting hours to days  and return    to usual state of health lasting weeks to months
Infant colic:
-paroxysms of irritability, or crying that start and stop without obvious cause
- episodes lasting 3 or more hours pre day and occurring at least 3 days per week for at least 1 week
Infant Dyschesia:
In a child less than 6 months old, must include:
- At least 10 minutes of straing and crying before successful passage of soft stools
Functional dyspepsia:
- Persistent or recurrent discomfort centered in the upper abdomen
- Not  relieved by defecation
-No evidence of an inflammatory or other causes that explains the symptoms
-Criteria fulfilled at least once per week for at least 2 months
Irritable bowel syndrome:
-Abdominal discomfort associated with two or more of the following
-Improvement with defecation
-Change in frequency of stool
-Change in form of stool
-No evidence of an inflammatory or other causes that explain the symptoms
-Criteria fulfilled at least once per week for at least 2 month
Functional diarrhea, functional constipation, aerophagia,  abdominal migraine, functional abdominal pain,   are other  functional  GI disorders.