Substitution
noun, の adjective, verbal noun
A substitute task is a substitution.
Note that this word has a slightly formal feel to it.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
マスタードの代用
a substitute for mustard
バターの代用
a substitute for butter
タバコの代用
a substitute for tobacco
サワークリームをヨーグルトで代用しました。
I substituted sour cream with yogurt.
このニンニクは、玉ねぎの代用ですか？
Is this garlic a substitute for onions?
オフィスチェアの代用で、バランスボールを用いる人がたくさんいます。
There are many people who use a balance ball in place of an office chair.