necessary and sufficient
Used in logic, mathematics, and formal contexts to describe conditions that are both required and enough. In everyday language, it can mean 'just right' or 'exactly what is needed'.
This condition is necessary and sufficient.
Please add a necessary and sufficient amount of water.
Compound of 必要 (necessary) and 十分 (sufficient). The exact historical derivation is uncertain, but it is a straightforward combination of two common Sino-Japanese words.