# When to use "in number" and when to use "in numbers"?

When talking about a quantity of people or things, I get 2 phrases "in number" and "in numbers". It's a little bit confusing for me, so I ask for help. These are some examples I got from online dictionaries

• We were eight in number(= there were eight of us).
• Letters of complaint were surprisingly few in number (= there were not many of them).
• The protesters were few in number, but they were very loud.

.

• Nurses are leaving the profession in increasing numbers.
• Newspapers are produced in vast numbers.
• To my mind, the construction to be XXX in number is almost always singular. It's very dated / literary with XXX=[numeric value], and the only other common value for XXX there is few (which isn't "marked" in the same way; it's still used a lot even today). On the other hand, the adjectival construction in YYY numbers is almost always plural. But a check with Google NGrams suggests that although my second "rule of thumb" there is true for almost all values XXX, the singular/plural choice is far less consistently implemented with in sufficient number/s.. Commented May 30, 2019 at 11:33
• @FF Worth an answer(?) Commented May 30, 2019 at 12:07

Nurses are leaving the profession in increasing numbers.

means the same thing as

Nurses leaving the profession are increasing in number.

In the first case, "in increasing numbers" is an adverb phrase describing how nurses are leaving the profession, as in "Nurses are leaving the profession without giving notice".

In the second case, "increasing in number" is an adjective phrase describing the nurses that are leaving the profession, as in "Nurses leaving the profession are predominantly experienced."

Per Merriam-Webster, there are a number of definitions of number—some of which take a singular form, and some of which take a plural form:

1. A sum of units: total, the number of people in the hall
2. Complement, the whole number of senators
3. An indefinite usually large total, a number of members were absent
4. numbers plural: a numerous group: Many numbers died on the way.
5. A numerical preponderance, There's safety in numbers

etc...

Your first 3 examples seem to be using one of the first 3 definitions.

Your 4th example (_nurses were leaving…in increasing numbers.) seems to be using Definition 4 (a numerous group of nurses).

Your last example seems to be using Definition 5 (Newspapers are produced in a numerical preponderance).