What are embeddings in vector search?

What Are Embeddings in Vector Search? Embeddings are numerical representations of data—like text, images, or audio—transformed into fixed-length vectors (arrays of numbers) that capture meaningful features or relationships. In vector search, embeddings act as a bridge between raw data and search algorithms, enabling efficient similarity comparisons. For example, a sentence like “a dog playing fetch” might be converted into a 300-dimensional vector where each dimension represents a latent feature (e.g., “animal,” “action,” or “object”). These vectors are stored in a database, and during a search, the system compares the query’s embedding to stored embeddings to find the closest matches. This approach bypasses traditional keyword-based methods, which struggle with semantic nuance, and instead relies on mathematical proximity in a high-dimensional space.

How Embeddings Work in Practice To generate embeddings, machine learning models—such as word2vec for text or CNNs for images—are trained to map data into vectors that preserve semantic or structural relationships. For instance, in natural language processing, the word “king” might be embedded near “queen” but farther from “car,” reflecting their conceptual similarities. During a search, similarity metrics like cosine similarity or Euclidean distance measure how close two vectors are. A practical example is a product recommendation system: if a user clicks on a shoe with an embedding emphasizing “sneakers” and “blue,” the system retrieves other items with embeddings near that vector. Tools like FAISS or Annoy optimize these comparisons at scale, enabling fast searches even across billions of vectors.

Use Cases and Considerations Embeddings power applications like semantic search engines (e.g., finding articles with similar themes), recommendation systems, or anomaly detection (flagging outliers in embeddings). A key challenge is balancing dimensionality: higher dimensions capture more detail but increase computational cost. For example, BERT-based text embeddings often use 768 dimensions, while simpler models might use 100. Developers must also handle model selection (pre-trained vs. custom) and storage—vector databases like Pinecone or Milvus specialize in managing and querying embeddings efficiently. While embeddings solve many search problems, they require careful tuning. For instance, mismatched training data (e.g., using a medical text model for movie recommendations) can lead to poor results. Overall, embeddings are a foundational tool for modern search systems but demand thoughtful implementation.