Smoking history is frequently expressed in the amount of packs per day times the number of years the person has been smoking. EXAMPLE: He stopped smoking 24 years prior to admission after approximately a 60-pack-year smoking history. So with this patient it could mean he smoked 1 pack per day for 60 years, or 5 packs per day for 12 years, or 6 packs per day for 10 years, or 2 packs per day for 30 years, etc. The above hyphen usage is the correct way to hyphenate this, although oftentimes people leave out the hyphen between pack and year. What is the correct way to express smoking history in terms of packs per day and number of years?