What is the difference between gharar and jahalah?

The Shari'ah (Islamic law) has prohibited buyu' al-gharar (transactions involving excessive uncertainty) and al-jahalah (ambiguity/ignorance) due to the injustice and animosity they entail. Gharar refers to a transaction whose outward appearance deceives the buyer, while its inner reality is unknown, or the sale of something with an unknown outcome. Jahalah is more general than gharar in that every gharar is a jahalah. However, gharar is more encompassing than jahalah in terms of the types of prohibited sales.

Transactions involving gharar are excepted when the uncertain element is included subordinately in the sale, or when such an amount is tolerated, either due to its insignificance or the difficulty in distinguishing it.