Briar
Part of speech: noun
Definition: Any of a number of unrelated thicket-forming thorny plants. A pipe made from the burl of the white heath tree.
Thorn
Part of speech: noun
Definition: A sharp protective spine of a plant.A letter of the Latin alphabet (capital: Þ, small: þ), borrowed by Old English from the futhark to represent a dental fricative, then not distinguished from eth, but in modern use (in Icelandic and other languages, but no longer in English) used only for the voiceless dental fricative found in English thigh