How do you make words ending in ful into plural?

Answer 1

It depends. Most of the time, you pluralise these words in exactly the same way you pluralise any other word ending in s. You add “es”. This is true for focuses, buses, pluses, minuses, and most other words. However, there are exceptions. Words that come from latin, such as stimulus, nucleus, and radius, still act as they did in latin. That is, they end in “-i”: stimuli, nuclei, radii. For some words (such as radius) it may be acceptable to use an “-es” ending for these in semi-formal contexts. Even to that rule there is at least one. Virus is a Latin word ending in “us”. It is pluralised as “viruses” and not as “viri” as you would expect a Latin word to be. This is because, as far as we know, the word virus had no plural in the Latin language. “Viri” meant “men”; and “virus” was treated in Latin as a mass noun (like “happiness”) which don’t, in standard usage, take a plural form.

Answer 2

There is no absolute rule here. Words derived from Latin and ending in -us often keep -i endings derived from Latin--alumnus, alumni--but these tend to disappear over time (think alums). Words without such origins follow the normal rules for words ending in -s--e.g., bus, busses.

Answer 3

Words ending in -ful are pluralised by simply adding an -s, e.g.:

teaspoonful - teaspoonfuls

spoonful - spoonfuls

cupful - cupfuls

Answer 4

The rules for making proper nouns plural are the same as for making common nouns plural; for example Gus would be two Guses, Gladys would be two Gladyses.