The decisive factor for children's clothing sizes is their body length, i.e. size 98/104 is suitable for a child who is approx. 95 - 106 cm tall. This can be seen as an approximate guideline. Ideally, you should simply measure, as not every child is "built" the same. If you want to give away children's outerwear such as shirts or sweaters, it is better to choose one or two sizes larger if in doubt. On the one hand, this looks more casual and on the other hand, the children will grow into it.