September 28, 2026 · 8 min read

What Is Semantic Search

A search box that matches words cannot tell that refund and get my money back mean the same thing, because the two share no letters. Semantic search closes that gap. It turns every document and every query into an embedding, a list of numbers that places meaning at a point in a large space and puts similar meanings nearby, then returns the documents whose points sit closest, measured by cosine similarity, the angle between two vectors on a scale from minus one to one. The idea runs from word2vec in 2013 through Sentence BERT in 2019, and Google folded it into Search in October 2019 to better understand one in ten queries. Across billions of vectors it stays fast through approximate nearest neighbor search, most often the hierarchical navigable small world graph. It does not replace keyword search, it joins it, and the pairing most teams ship is hybrid search.