What is the appropriate usage for “less than”?

"Less than" is correctly associated with uncountable nouns, which are nouns that cannot be counted individually or do not have a plural form, such as "water," "sugar," and "information." The phrase is utilized to indicate a quantity or amount that is smaller than a specified number or quantity. When discussing measurements, amounts, or degrees that are collective and not quantifiable in distinct individual units, "less than" is the appropriate choice.

In contrast, the other options focus on countable nouns or abstract concepts like emotions and feelings, which do not apply to the usage of "less than" as effectively. Countable nouns would use "fewer than" to indicate a smaller number of distinct items. Hence, the use of "less than" aligns perfectly with the context of uncountable nouns, making it the correct choice.