The oxidation state of an atom is the fictitious charge that an atom would have if all bonds between atoms of different elements were 100% ionic. Thus, oxidation is better defined as an increase in oxidation state, and reduction as a decrease in oxidation state.
Most babies take their first steps sometime between 9 and 12 months and are walking well by the time they're 14 or 15 months old. Don't worry if your child takes a little longer, though. Some perfectly normal children don't walk until they're 16 or 17 months old.
By 15 months the average child is pretty good at walking and likes to push and pull toys while he toddles. At about 16 months, your child will begin to take an interest in going up and down stairs -- though he probably won't navigate them solo for a few more months. Most 18-month-olds are proficient walkers.