pen (Noun) — A writing implement with a point from which ink flows.
pen (Noun) — An enclosure for confining livestock.
pen (Noun) — A portable enclosure in which babies may be left to play.
pen (Noun) — A correctional institution for those convicted of major crimes.
pen (Noun) — Female swan.
pen (Verb) — Produce a literary work. ex. "He penned four novels"
pen (Verb) — Enclose or keep in a pen.