# What is Semantic Routing? Definition & Technical Mechanics

> **Source:** [SPIDITS AI AI Glossary](https://spidits.com/ai-glossary)  
> **Category:** Agentic Systems  
> **Canonical Citation:** [https://spidits.com/ai-glossary/semantic-routing](https://spidits.com/ai-glossary/semantic-routing)

## Definition
Semantic Routing is an architectural technique that routes incoming prompts or API queries to specialized LLM models, vector databases, or cached responses based on intent and embedding similarity, rather than static keyword rules.

## Architectural Mechanics & Deep Dive
Semantic routing acts as an intelligent traffic gateway for modern LLM applications. Instead of executing every request against a high-cost frontier model, a semantic router converts incoming prompt text into a vector embedding and compares it against pre-defined intent clusters. Depending on vector distance, the system routes the request to the most cost-effective endpoint.

## Industry Applications & Real-World Use Cases
Optimizing inference cost, latency reduction, and multi-model router orchestration

## Frequently Asked Questions

### How does semantic routing reduce LLM API costs?
By evaluating prompt embeddings, a semantic router directs simple queries to lightweight models or instant cache hits, reserving large frontier models for complex multi-step reasoning.

### What is the difference between keyword routing and semantic routing?
Keyword routing relies on exact phrase matches, whereas semantic routing uses vector embeddings to understand intent even when queries use synonyms or alternative phrasing.

## Related Terminology
- [llm](https://spidits.com/ai-glossary/llm)
- [vector-database](https://spidits.com/ai-glossary/vector-database)
- [agentic-ai](https://spidits.com/ai-glossary/agentic-ai)

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