Three retrieval styles: Lexical (BM25 / TF-IDF) — matches exact terms; unbeatable for precise identifiers like gene symbols (BRCA1), rsIDs (rs80357906), and HGVS notation Dense (embeddings) — catches paraphrase and synonymy ("breast cancer risk gene") Hybrid — runs both and fuses the results (e.g., Reciprocal Rank Fusion), or re-ranks the union Genomics specifically benefits from hybrid, because so much of the signal is exact codes that embeddings blur together.