Use the word "plenty" when an amount is large enough to satisfy a need. You can pronounce this word as "plenty," with the "t" sound, or as many Americans do, "pleny," without the "t" sound.
There’s plenty of time to get to the airport. We don’t have to rush.
Mario has plenty of friends who can help him.
There’s plenty to see at the museum.
The children will have plenty to do at the birthday party.
We had plenty to eat at the banquet.
The United States is a land of plenty. We’re very lucky to be so fortunate.
The word "plentiful" is an adjective:
There’s a plentiful supply of fresh fruit and vegetables for our local grocery store.
Land available for farming is plentiful in this part of the country.
Notice that the word "plenty" is often followed by the preposition "of" or an infinitive. However, in spoken English, some people use "plenty" as an adverb to mean "very." I don’t recommend this, but you might hear it used:
He felt plenty tired after running in the marathon.
I’m feeling plenty hungry.
She’s plenty mad about this situation.
There’s plenty to choose from at the farmers market.