What are embeddings in machine learning?

Embeddings in machine learning are vector representations that map complex, high-dimensional data—like text, images, or categorical variables—into a lower-dimensional continuous space. These representations are learned during training to capture meaningful patterns or relationships in the data. For example, words in natural language processing (NLP) are often converted from sparse one-hot encoded vectors into dense embeddings where similar words (e.g., “cat” and “dog”) occupy nearby positions in the vector space. This makes embeddings a powerful tool for translating raw data into a form that algorithms can process more effectively.

Embeddings are typically created by training a model to adjust the vector values based on observed data. In NLP, models like Word2Vec or GloVe generate word embeddings by analyzing co-occurrence patterns in text: words appearing in similar contexts get similar vectors. Similarly, recommendation systems use embeddings to represent users and items (e.g., movies or products). Here, embeddings are trained so that users and items they interact with are closer in the vector space. For instance, a user who watches sci-fi movies might have an embedding near the embeddings of sci-fi films. Beyond text and recommendations, embeddings can also represent images (using CNN features), graph nodes (for social networks), or even tabular data categories, enabling cross-domain applications like searching for similar products based on user behavior.

The key advantage of embeddings is their ability to encode semantic or relational information efficiently. By reducing dimensionality, they mitigate computational bottlenecks (e.g., handling millions of unique categories) while preserving critical relationships. For developers, implementing embeddings often involves using libraries like TensorFlow or PyTorch, which provide embedding layers that map discrete inputs to vectors. Practical considerations include choosing the embedding dimension (e.g., 50–300 units for text) and deciding whether to use pre-trained embeddings (like BERT for NLP) or train task-specific ones. Visualization tools like t-SNE or PCA can help inspect whether embeddings capture meaningful patterns. For example, plotting word embeddings might reveal clusters for animals or colors, validating their quality. Embeddings are foundational in modern ML pipelines, enabling models to generalize better and handle unstructured data at scale.