less vs. fewer (idea)

Many people misuse "less", when "fewer" would be the correct word to describe a reduced or lower quantity. Here is the rule used in modern English (although see Gritchka's writeup in "fewer"):

• "Less" is to be used when the quantity being described is continuous, as in "This bucket contains less water than that one".
• "Fewer" is to be used when comparing two discrete amounts, as in "There are fewer female E2 users than male".

Commonly misused in supermarket express checkout queues: "10 items or less".