One-sentence definition
Information retrieval based on meaning relationships, usually combined with filters or lexical search.
How to interpret this concept
Semantic search attempts to retrieve information based on the meaning relationship between query and content, not just word matches. A common technique uses embeddings and compares vectors. Its usefulness depends on the model representing the language, specialized vocabulary, and type of question of the application well.
It does not always replace lexical search. An invoice identifier, a function name, or a legal reference may require exact match. A hybrid search combines lexical and semantic signals; a reranker can then order a reduced set of candidates. These are distinct stages and must be measured separately.
Practical example: in an architecture manual, thermal bridges may be relevant to a query about heat loss even if the vocabulary differs. To evaluate this, prepare real queries with identified relevant documents and measure which appear among the top results. The similarity score is not a probability of truth and should not be presented as such.
