What is the difference between 未満 and 不足? Both and have the meaning of insufficient in JMDict. What is the difference in their usage?

: it expresses **value**. e.g. 20 means 'less than 20 years old'. means 'He is beyond a friend but not to the level of a boyfriend.'

: It expresses **status**. It is necessary indeed, but it is insufficient now (and you would like to fulfill soon.). e.g. means 'you have not studied enough and you have to study more'. means 'You have a sub-optimal level of vitamins' (because you have not taken in enough vitamins).