Customer language
Use search behavior to reduce the distance between catalog and customer vocabulary.
Keeping source data clean
Do not put every search variant in product titles.
Synonyms layer
Explicitly manage equivalent or related terms.
One-way relations
Not every synonym has to have both sides on the same meaning.
Local terms
Manage regional choice of words by language or market when needed.
Monitoring
Use zero-result searches and reformulations to discover new customer language.