IPA: //ˌsɛkstəʊˈdɛsɪmoʊ//
KK: /sɛkstəˈdɛsɪmoʊ/
A type of book size that is made up of pages folded into sixteenths, resulting in a smaller format.
The library has a collection of rare sextodecimo books.
Sextodecimo → It is formed from "sexto-" (from Latin "sextus", meaning sixth) and "decimo" (from Latin "decimus", meaning tenth). The word refers to the sixteenth in a series, specifically in the context of book sizes or page numbering.
Think of 'sixth' ('sexto-') and 'tenth' ('decimo') to remember that 'sextodecimo' means the sixteenth in a sequence.
No commonly confused words.