Borel measure

{{quote-book|en|author=Gerald B. Folland|title=Real Analysis: Modern Techniques and Their Applications| edition=Second| location=New York| publisher=John Wiley & Sons, Inc.| year=1999| section=§1.5| page=33| isbn=978-0-471-31716-6| oclc=803988029| text=We are now in a position to construct a definitive theory for measuring subsets of ℝ based on the idea that the measure of an interval is its length. We begin with a more general (but only slightly more complicated) construction that yields a large family of measures on ℝ whose domain is the Borel σ-algebra ℬ_ℝ; such measures are called Borel measures on ℝ.}}