Within a listing, not all keyword placements carry equal weight for the A9 algorithm:
This informs how Helium 10 Listing Builder copy should be sequenced: highest-priority main keywords go first in the title, and multi-word phrases should be kept intact rather than broken up.
Stated directly: "the keywords you include in the title carry the most weight... And the keywords closest to the beginning of the title have more weight." In practice: order title keywords by priority/search volume and place the top terms as close to the start as possible, pushing overflow into bullets/description (see Helium 10 Listing Builder).
Because a human shopper reads the title, not just the algorithm, title construction has to balance keyword position against readability: the shortest, most relevant keyword phrase should lead the title, but stuffing additional keywords past that point degrades conversion even if it doesn't hurt indexing. A title that reads as a keyword dump signals a low-quality listing to a human buyer regardless of what it does for A9 relevancy matching.
A specific claim (from 6 Steps to a Perfectly Optimized Amazon Listing): the first five words of a title carry outsized weight both for Amazon A9 Algorithm indexing and for human shoppers, since most people scanning search results don't read past the first few words of a title. Practically this means front-loading the highest-value keywords that also clearly state what the product is and who it's for — not burying them behind brand name or filler.
Related: the keyword-stuffing side of the same title is covered in Keyword Repetition De-Indexing Penalty (no more than ~2 repeats of a given keyword in the title).
A keyword earns Amazon's top relevancy score only when it appears in the listing in its exact written form, ideally early in the title. Broad or plural variants of the same phrase — even ones a human would read as synonymous — earn a lower relevancy score, because the matching compares strings rather than inferring intent.
Apply: write the target keyword phrase verbatim and near the front of the title (e.g. "toiletry bag for men," not just "men's toiletry bag") rather than trusting broad match to pick up credit for the exact phrase.