Mostly conjecture and original research: A parcel has the modern connotation of being sent by mail, and you normally never hear of the noun used to describe anything else (though you may sometimes hear it in verb form, meaning "to deliver in regular, divided amounts"). The word originated from the Old French parcelle meaning "a small piece or part". A package also generally has the same connotation. The word evolved from "pack" which has its roots in Old German, to basically mean "the product of packing" similar to the etymology of "baggage". While a package is often sent by mail, you could hear of a "package" being stored, or of a "gift-wrapped package" being delivered in person. A packet is a newer word, with forms first appearing in the 1500s (vs the 1200-1300s) in Middle French (pacquet). The word originally meant "bundle", but now typically has one of the following connotations: A small envelope containing spices, grain, seed, or similar material. A collection of papers or other information, often bound, as in the written material for a presentation. A chunk of data sent over a network. src: english.stackexchange