picnic / pyknic 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. 👇
picnic: (noun) any informal meal eaten outside or on an excursion. (verb) eat alfresco, in the open air.
pyknic: NA
picnic: p·IH·k·n·IH·k
pyknic: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)