What is the difference between society wardship and a parent losing decision-making responsibility?

These come from two different statutes and mean different things. Wardship - a child becoming a society ward or Crown ward - is a status a child protection court can impose under the Child, Youth and Family Services Act, 2017 after finding a child is in need of protection; it places the child under a children's aid society's, or the Crown's, care and authority, on a temporary or, in serious cases, a more permanent basis, and can displace a parent's day-to-day care of the child almost entirely for as long as it lasts.

Losing "decision-making responsibility" is a family law outcome under the Divorce Act or the Children's Law Reform Act, made in the parents' own parenting case - a family court decides that one parent, not the society, should hold authority over the child's major decisions such as health, education, and religion, while the other parent may still have parenting time. A parent can lose decision-making responsibility to the other parent with no CYFSA finding involved at all, and a child can become a ward without the family court's own order changing until that order is separately reviewed. The two proceedings don't automatically update each other.