Q. When referring to decimals from zero to one, are they singular or plural? For example, “The road extends for 0.8 mile(s).” A coworker is arguing it is singular since it is not more than one, while I believe it to be plural since we are now talking about multiple pieces of one (eight tenths). If it is singular does the same hold true for similar numbers written as fractions?

A. Decimal quantities are considered to be plural; quantities expressed as fractions are considered to be singular. So write “0.8 miles” but “eight tenths of a mile.” For decimal forms, only the number one is singular: 1 mile. Once you add a decimal, even if it’s a zero, it becomes plural: 1.0 miles. See CMOS 9.19.