pronoun
some, many a
A2
manch is an indefinite determinative/pronoun meaning some, many a, or several. Often used attributively before nouns (e.g., mancher Tag) and as pronoun (manch einer). It declines like an adjective (manch-, manche, manchem). More formal or literary than everyday 'einige' or 'viele'; common in written registers.
Examples
Manch einer mag diesen Film nicht.
Some people may not like this film.
Da manch einer die Hinweise übersah, kam es zu Missverständnissen, die später geklärt wurden.
Because some people overlooked the instructions, misunderstandings occurred that were clarified later.
Manch ein Schüler war überrascht.
Many a student was surprised.
Details
Mnemonics
Imagine a row of items and someone pointing to 'manch' (some of them)
manch sounds like 'much' — remember it's about quantity
Notes
Used in slightly literary or formal registers in some constructions (e.g., 'Manch einer').