Quick Answer. An experimental variable is something that a scientist changes during the course of an experiment. It is distinguished from a controlled variable, which could theoretically change, but the scientists keep constant. Continue Reading.
While you were pregnant, your baby developed tooth buds, the foundation for baby teeth (also called milk teeth). Very rarely, a baby is born with a tooth or two, or grows a tooth in the first few weeks of life. But the vast majority of babies sprout their first tooth sometime between 4 and 7 months old.
Babies may begin teething as early as 3 months old, or well after their first birthday, but 6 months of age is a fairly common time for teething to begin. Your child's behavior may clue you in to when it's almost time for a tooth to emerge, or erupt, through the gums. Babies are often fussy for up to five days or so before a tooth breaks through. Their gums become tender, sore and swollen.