Is one pig called a swine?

Answer 1

One pig can be called a swine, or many pigs can be called swine, the same as with "hair", "fish", or "deer", since these words all use the identical word as both the singular and the plural forms of the words.

According to most dictionaries, and as outlined in various grammar sources:

"Nouns with identical singular and plural forms

Some nouns have identical singular and plural forms. Examples are: sheep, swine, aircraft, spacecraft, series, species, pair etc." ~ Englishpractice.com

(see link below in the related links section)

Some people, and perhaps some dictionaries, prefer to use the word swine to mean only a plural form of pig or hog. Other plural forms of pig and hog are "pigs" and "hogs". There are some people who say that using swine as the singluar form "...is very old-fashioned and possibly obsolete", but either way is actually still correct grammatically.