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.
What is teething? Your baby is teething when his or her first set of teeth, called primary teeth, break through the gums. When does teething typically start? Teething usually begins around 6 months of age. But it is normal for teething to start at any time between 3 months and 12 months of age. By the time your child is about 3 years old, he or she will have all 20 primary teeth. The lower front teeth usually come in first.