Use 'plentiful' in discussions about availability and abundance, especially in natural or economic resources contexts. Wild berries are plentiful in the forest during summer.
Pro Tip 2/3
Positive Connotation
'Plentiful' often implies a positive situation where lack or need is absent. Thanks to the rain, the harvest was plentiful this year.
Pro Tip 3/3
Quantifiable Subjects
Use 'plentiful' when discussing things that can be quantified or measured, not for abstract concepts. Fish are plentiful in these waters.