Shortage
Insufficiency
noun, な adjective, verbal noun
You have something that's not sufficient. When something isn't sufficient, you have an insufficiency or shortage.
This word is more commonly used in formal contexts. In more casual, everyday conversations, 足りない is often preferred to express something being insufficient.
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.
このエリアでは去年、水が不足しました。
Last year, there was a water shortage in this area.
不正アクセスがあったのは、わたしの力不足のせいです。すみませんでした。
There has been unauthorized access due to my insufficient skills. I'm sorry.
この不足分は、どこで生まれたんだろう?
Where is this portion of the shortage coming from?