Add section about Enumerable#lazy

README.adoc

@@ -4950,6 +4950,28 @@ LOREM
 "when an unknown printer took a galley of type and scrambled it to make a type specimen book."
 ----
 
+== Enumerable
+
+=== lazy [[lazy]]
+
+Use `Enumerable#lazy` in combination with methods like `.first` or `.take`, especially for operations on large collections or datasets, because it avoids the need to process the entire collection.
+
+[source,ruby]
+----
+SIZE = 10
+MAX = 10_000_000
+
+# bad
+(0..MAX).uniq { |x| x + 2 }.first(SIZE)
+(0..MAX).map { |x| x + 2 }.first(SIZE)
+(0..MAX).select { |x| x + 2 }.take(SIZE)
+
+# good
+(0..MAX).lazy.uniq { |x| x + 2 }.first(SIZE)
+(0..MAX).lazy.map { |x| x + 2 }.first(SIZE)
+(0..MAX).lazy.select { |x| x + 2 }.take(SIZE)
+----
+
 == Heredocs
 
 === Squiggly Heredocs [[squiggly-heredocs]]