The decade of the 1940s. / Temperatures from 40 to 49 degrees.

plural of 40 (“bottle of beer”)

Alternative spelling of 40s

(molecular biology) The small subunit of the eukaryotic 80S ribosomes.

(US, slang) A bottle containing 40 fluid ounces of malt liquor beer.

plural of top 40

(physics) A naturally-occurring radioactive isotope of potassium, ⁴⁰₁₉K, having nineteen protons and twenty-one neutrons, and a half-life of 1.3 billion years; it is the chief source of natural radioactivity in living tissue

(physics) The major stable isotope of argon, ⁴⁰₁₈Ar, having eighteen protons and twenty-two neutrons; it amounts to about 99.6% of the element in nature

(physics) The major stable isotope of calcium, ⁴⁰₂₀Ca, having twenty protons and twenty neutrons; it amounts to almost 97% of the element in nature

(music, radio) A radio format for popular music, usually including the 40 most popular songs at a given time.