All information retrieval models are based on the equality which exists between the query terms and the documents terms. This principle is based on the assumption that terms are correctly extracted from the documents and queries. But in some context (such as document generated by automatic speech recognition or by optical character recognition systems), this assumption is not true. We propose a generalisation of the information retrieval model based on the language model integrating this dimension. To do it, we introduce two notions: the term certainty value (in relation with the extraction process) and the pairing between two terms. Pairing between two terms is defined by their relative position (called the concordance) and the area they have in common (called the intersection).