Embeddings are the foundation of modern NLP, enabling machines to work with human language in a mathematically meaningful way.
Understanding how to create, use, and optimize embeddings is essential for any text-processing application.
Embeddings are numerical representations that transform discrete tokens (words, subwords, characters) into continuous vector spaces.
Think of them as a way to give computers a mathematical understanding of language meaning.
Key Characteristics:
- Dense vectors: Each embedding is a list of real numbers (typically 100-4096 dimensions).
- Semantic capture: Similar words have similar embeddings in vector space.
- Contextual: Modern embeddings consider surrounding context, not just the word itself.
- Fixed dimensionality: All embeddings from a model have the same number of dimensions.
Alternative names: embedding vectors, vector representations, dense representations, distributed representations
By converting words to vectors, we enable:
- Semantic similarity: Measuring how similar two pieces of text are.
- Machine learning: Using text as input to neural networks.
- Information retrieval: Finding relevant documents or passages.
Types of Embeddings
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Token Embeddings
- Scope: Individual tokens (words, subwords, characters).
- Use case: Building blocks for language models.
- Example: "language" → [0.1, -0.1, 0.2, ..., 0.3]
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Sentence Embeddings
- Scope: Complete sentences or short passages.
- Use case: Semantic search, text classification, clustering.
- Example: "Hello Embeddings!" → [0.4, -0.3, 0.7, ..., 0.8]
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Document Embeddings
- Scope: Entire documents or long passages.
- Use case: Document classification, recommendation systems.
Contextual vs. Static Embeddings
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Static Embeddings (Word2Vec, GloVe):
Same vector for a word regardless of context.
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Contextual Embeddings (BERT, GPT, etc.):
Different vectors based on surrounding context.
Training Process
- Initialization: Start with random vectors for each token.
- Context learning: Model learns from massive text datasets.
- Optimization: Vectors adjust to capture semantic relationships.
- Convergence: Final embeddings encode learned patterns.
Practical Applications
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Text Generation
- Language models use embeddings as input representations.
- Enable models to understand and generate coherent text.
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Text Classification
- Convert documents to embeddings.
- Train classifiers on vector representations.
- Examples: sentiment analysis, spam detection.
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Semantic Search & RAG
- Convert queries and documents to embeddings.
- Find similar content using vector similarity.
- Power recommendation systems and search engines.
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Text Clustering
- Group similar documents using embedding similarity.
- Organize large text collections.
- Discover hidden themes in data.
Strategies for combining token embeddings into sentence embeddings:
- Mean pooling: Average all token vectors.
- Max pooling: Take maximum value across each dimension.
Model Selection
- General purpose: all-MiniLM-L6-v2, all-mpnet-base-v2.
- High performance: all-MiniLM-L12-v2, larger models.
- Domain-specific: Fine-tuned models for medical, legal, scientific text.
- Multilingual: paraphrase-multilingual-MiniLM-L12-v2.