In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam Muhammad Ibn Saaleh al-Uthaymeen [rahimahullaah] said:
Knowledge (Ilm) is to comprehend the reality of something as it truly is, with certainty.
The levels of comprehension are six:
[Al ‘Ilm – Knowledge], which is to comprehend the reality of something as it truly is, with certainty.
[Al Jahlul Baseet- slight ignorance], which is absence of full comprehension.
[Al Jahlul Murakkab-, Aggravated/compounded ignorance], which is to comprehend something in a way contrary to its true reality.
[Al Wahm – Delusion], which is to think that one comprehends something despite the presence of that which should cause you to realize that you are incorrect.
[Ash Shakk- Doubt], which is to think that you comprehend something, yet you are aware of something contrary to it which you think has the same possibility of being the truth.
[Dhann – Preponderant belief], which is comprehension of something, despite the presence of something which is contrary to it, but which is less likely to be true.
[Source: Sharh Usool Ath-Thalaatha- Explanation of the three fundamental principles. English Translation pages 37. By Shaikh Abu Talhah (may Allaah have mercy upon him and his wife Aameen)]