Similarity-Based Finite-State Lookup. Error-tolerant lookup of words in large vocabularies has many potential uses, both within and beyond natural language processing (NLP). SILO is a generic library for finite-state-based lexical lookup, originally designed for NLP-related applications, that can be adapted to application-specific error metrics. Among other things, this tool can be used for searching existing trademarks in a database, using orthographic and phonetic similarity.