adjective
numerous, many
B1
Zahlreich is an adjective meaning 'numerous' or 'many'. It is gradable: comparative zahlreicher, superlative am zahlreichsten. Used attributively and predicatively like other adjectives; no irregular forms. Can appear with prepositions (e.g., zahlreich an Teilnehmern) but otherwise behaves regularly in declension.
Examples
Auf dem Festival gab es zahlreiche Stände, die regionale Produkte anboten, sodass viele Besucher blieben.
At the festival there were numerous stalls offering regional products, so many visitors stayed.
Es gibt zahlreiche Gründe dafür.
There are numerous reasons for that.
Zahlreiche Gäste kamen zur Feier.
Many guests came to the party.
Details
Mnemonics
a crowd filling a stadium to show a large, numerous group
think 'zahl' (number) + 'rich' — rich in numbers = numerous
Notes
Commonly used in written and spoken German to indicate a large, countable quantity. Can be inflected (zahlreiche, zahlreicher).