A synonym group (previously referred to as a "two way synonym") is a collection of words or phrases that are considered equivalent in meaning for the purposes of search. Synonym groups are used to return relevant results even if the search query uses different terminology than what is in the index.
For example, if a synonym group contains the phrases "0% milk," "skim milk," and "nonfat milk," a search for any of these terms would return results related to all three, recognizing them as equivalent in meaning.
Synonym groups are transitive, meaning that if A is a synonym for B, and B is a synonym for C, then A is a synonym for C. They are designed to be case insensitive and to match the exact word ordering when using phrases.
Specific to index
Synonym groups are set on each index key separately, so a customer can have separate synonym rules for two independent properties, such as their Dutch and French grocery stores.
Case insensitive
Synonyms ignore case, so a synonym rule for fat-free milk would apply to McCormick's Farmstand Fat-Free Milk as well as McCormick's farmstand fat-free milk
Exact phrase matching
Synonyms match the exact word ordering, so a rule for 0% milk would not apply to products McCormick's Farmstand Milk 0% or McCormick's Farmstand 0% fat milk. To match these products, synonyms for milk 0% or 0% fat milk would need to be included in the group
Transitive
All synonyms within a group are transitive. Fat-free searches return 0% milk and skim milk products, skim milk searches return 0% milk products and vice-versa.
However, a separate group containing non-fat milk and skim milk would not establish equivalence between non-fat milk and 0% milk by virtue of the separate group establishing the skim milk relationship.