instead of; in place of; replacing
Used when someone or something takes over a role, duty, or position from another. Often implies substitution.
See also: にかわり
The vice president attended the meeting instead of the president.
New machines were introduced, replacing the old ones.
Used when acting for someone else, often in a representative or proxy capacity. Can overlap with sense 1 but emphasizes acting in someone's interest rather than simple replacement.
On behalf of my mother, I would like to express our gratitude.