Plenty means more than enough. There is plenty of time, plenty of room, we have plenty. It is warm and reassuring, which is why it is the word people reach for when telling somebody not to worry.
The grammar is worth care. Plenty of goes before both countable and uncountable nouns — plenty of chairs, plenty of water — and plenty on its own is a pronoun: there is plenty. It is not usually used in questions or negatives, where enough or much go instead: not much time, not plenty of time. As an adverb it is informal: it is plenty big enough. The adjective plentiful describes a supply rather than an amount.
1nounplentyMore than enough of something.
“There is plenty of room for everybody.”
2pronounlargeA large enough amount.
“Do not buy more — we have plenty.”
3adverbuseIn informal use, quite or amply.
“The bag is plenty big enough for a weekend.”
Too few real examples of this word to estimate which sense is commonest.
plenty is an amount.
Also accepted in games: ample
Latin plenitatem meant fullness, from plenus, full — the same root as plenary, replete, complete and plus. Plenty is fullness, and the sense of abundance follows straight from a full container.
Proto-Indo-European
*pleh₁-
Proto-Indo-European
*pl̥h₁nós — full
Latin
plēnitātem
Old French
plenté
Anglo-Norman
plenté
Middle English
plentie
English, today
plenty
Built from
From plent(é) + -y, from Middle English plentie, plentee, plente, from Anglo-Norman plenté, from Old French plenté, from Latin plēnitātem, accusative of plēnitās (“fullness”), from plenus (“complete, full”), from Proto-Indo-European pl̥h₁nós (“full”), from which English full also comes, via Proto-Germanic. Related to the Latin derivatives replenish, plenary, complete, deplete, replete.
Etymology from Wiktionary, CC BY-SA