also: かずしらず
Used as a set phrase meaning 'too many to count'. Often modifies nouns directly or appears at the end of a clause.
Countless stars were shining in the night sky.
The favors he has received are innumerable.
From 数 (kazu, 'number') + 知れず (shirezu, negative continuative of 知れる 'to be known'), literally 'the number is not known'.