# What is Bidirectional LSTM? Definition & Technical Mechanics

> **Source:** [SPIDITS AI AI Glossary](https://spidits.com/ai-glossary)  
> **Category:** Neural Architectures  
> **Canonical Citation:** [https://spidits.com/ai-glossary/bidirectional-lstm](https://spidits.com/ai-glossary/bidirectional-lstm)

## Definition
A Bidirectional LSTM (BiLSTM) is a sequence processing architecture that consists of two LSTMs: one taking the input in a forward direction, and the other taking it in a backward direction. This allows the network to capture both past and future context at any point in the sequence.

## Architectural Mechanics & Deep Dive
A Bidirectional LSTM (Long Short-Term Memory) is a recurrent neural network architecture that processes sequential data in both forward and backward directions. By using two independent hidden layers, it captures both past context (words before) and future context (words after) at any given point in the sequence. This bidirectional context is highly valuable for tasks like named entity recognition and machine translation where local context depends on surrounding text.

## Industry Applications & Real-World Use Cases
Named entity recognition, speech recognition, and translation alignment.

## Frequently Asked Questions

### What advantage does BiLSTM have over standard LSTM?
Standard LSTM only has access to past context. BiLSTM looks at both the words before and after a target word, resulting in a deeper contextual understanding.

### Is BiLSTM used in generative models?
No, because generative models cannot look ahead into the future tokens they have not generated yet. They are primarily used for understanding and labeling tasks.

## Related Terminology
- [lstm](https://spidits.com/ai-glossary/lstm)
- [recurrent-neural-network](https://spidits.com/ai-glossary/recurrent-neural-network)
- [neural-network](https://spidits.com/ai-glossary/neural-network)

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*From the SPIDITS AI Knowledge Base (336+ terms indexed). Explore full technical definitions: [https://spidits.com/ai-glossary](https://spidits.com/ai-glossary)*