cygnet / signet are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
cygnet: (noun) a young swan.
signet: (noun) a seal (especially one used to mark documents officially).
cygnet: NA
signet: s·IH·g·n·ih·t
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)