GLOSSARY

Key Sentence

A key sentence is the most relevant sentence picked from a page to summarize it. In search, it powers the snippet that explains why a result matches your query.

What is a Key Sentence?

A key sentence is a short, representative sentence selected from a document that best answers the query or summarizes the page. Search systems use it to build snippets that boost understanding and click-through.

How It Works (quick)

  • Segment: Split content into sentences; strip boilerplate, ads, and nav text.
  • Score: Rank sentences by query overlap (BM25/TF-IDF), coverage of entities/attributes, and/or embedding similarity.
  • Select & highlight: Pick the top sentence; bold matched terms; truncate safely for mobile.
  • Fallbacks: If no strong candidate, fall back to meta description or a generated summary (with guardrails).
  • Cache: Store per (query, page) pair for popular queries.

Why It Matters in E-commerce

  • Higher CTR: Clear snippets reduce guesswork on the SERP or site search.
  • Reduced pogo-sticking: Shoppers understand fit, material, compatibility before clicking.
  • Support answers: Help-center snippets surface the exact policy or step.

Best Practices

  • Prefer query-biased extraction over generic summaries.
  • Pull from visible, indexed text; avoid hidden or legal-only blocks.
  • Keep brand/model/size tokens intact; preserve casing (e.g., GORE-TEX).
  • Enforce length limits (e.g., 160–200 chars desktop, ~110–140 mobile).
  • Localize sentence splitting and punctuation rules per language.
  • Log chosen sentences and confidence for QA.

Challenges

  • Bullet lists and tables aren’t sentence-like; handle gracefully.
  • JavaScript-only content may be invisible to crawlers.
  • Generated snippets can drift; keep them grounded in retrieved text.

Examples

  • Query “waterproof trail jacket”: snippet shows “Lightweight GORE-TEX shell with sealed seams and helmet-compatible hood.”
  • Query “return period”: snippet shows “You can return items within 30 days of delivery.”

Summary

Key sentences turn pages into crisp, query-relevant snippets that lift CTR and trust. Extract from visible content, bias to the query, and enforce length and brand/size fidelity.

FAQ

Key sentence vs meta description?

Meta is page-authored; a key sentence is algorithmically chosen per query.

Can we use LLMs to generate snippets?

Yes, but ground them in retrieved text and cite spans to avoid hallucinations.

Multiple key sentences?

Use one primary and a backup; avoid clutter in the SERP card.