Which abbreviation means "as far as I know"?

The abbreviation that means "as far as I know" is indeed the one that stands for AFAIK. This phrase is commonly used in both spoken and written communication to indicate that the speaker is sharing information that is based on their current knowledge or understanding, while also implying that their knowledge may be limited or not all-encompassing. Using AFAIK allows for clear communication while maintaining humility about the completeness of the information being conveyed.

The other abbreviations serve different meanings: AFAIC (as far as I'm concerned) expresses a personal opinion rather than knowledge, AFAIUI (as far as I understand it) relates to understanding rather than knowledge, and AFAICT (as far as I can tell) suggests an observation rather than knowledge. Each of these expressions may convey related but distinct nuances, underscoring the importance of accurate use of abbreviations in communication.