  Hallucination in a foundation model (FM) refers to the generation of content
that strays from factual reality or includes fabricated information. This
survey paper provides an extensive overview of recent efforts that aim to
identify, elucidate, and tackle the problem of hallucination, with a particular
focus on ``Large'' Foundation Models (LFMs). The paper classifies various types
of hallucination phenomena that are specific to LFMs and establishes evaluation
criteria for assessing the extent of hallucination. It also examines existing
strategies for mitigating hallucination in LFMs and discusses potential
directions for future research in this area. Essentially, the paper offers a
comprehensive examination of the challenges and solutions related to
hallucination in LFMs.
