Plural of “swine”

The plural of swine is swine.

Why

Long before it narrowed into a mostly formal or agricultural term, 'swine' (Old English 'swin') was simply the everyday word for pigs, and its identical singular and plural forms go back to the same quirk of Old English grammar that left 'sheep' and 'deer' unmarked for number: certain neuter nouns in that grammatical class never had distinct plural endings to begin with.

"Swine" has narrowed considerably in everyday use, largely replaced by "pig" and "hog" in casual farming and food vocabulary (both of which pluralize fully regularly as "pigs" and "hogs"), leaving "swine" concentrated mainly in formal agricultural, veterinary, and scientific writing ("swine flu," "swine production"), as well as in older or dialectal speech. The word carries an unusually strong negative figurative connotation compared to most other zero-plural farm animals, historically used as a genuine insult in English long before "pig" took on a similar negative figurative sense, a cultural pattern that developed independently of, though sometimes confused with, the grammar of the word's unchanging plural form.

Usage note

"Swine" never takes -s in any register; it remains fixed whether describing a single animal or an entire herd, matching the same behavior as "sheep" and "deer," though it's far less common in ordinary conversation than either of those more everyday zero-plural animal names.

"Swine flu," the popular name for the influenza strain first linked to pigs, holds "swine" fixed and unchanging inside the compound no matter how many outbreaks or regions come up in discussion — functioning here purely as a descriptive label rather than a countable noun. Public health officials settled on "swine" specifically when naming the 2009 H1N1 outbreak, a term some agricultural groups later pushed back against over its economic fallout for pork producers, even though the compound was simply pointing to the disease's animal origin rather than casting judgment on the industry. Medical research, meanwhile, turns to swine constantly because their cardiovascular systems closely mirror human ones, making them valuable stand-ins for testing certain devices and surgical procedures.

Common real mistakes

"Swines" counts as a genuine error, though a rare one in practice, since the word itself rarely surfaces outside formal agricultural or scientific writing. A separate, unrelated confusion involves the insulting figurative sense of "swine" applied to a contemptible person — that use, too, stays frozen in the zero-plural form no matter how many people the insult is aimed at. Worth noting as well: "swineherd," an older compound naming someone who tends pigs, carries "swine" through unchanged inside the compound no matter the size of the herd being tended, the same freezing pattern found in many English compounds anchored to an invariant root noun.

The wider pattern

"Swine" belongs to the same closed group of ancient Old English zero-plural animal nouns as "sheep" and "deer," all reflecting a grammatical gender pattern that made singular and plural identical long before most other English nouns settled into the regular -s pattern.

Examples

• The farm raised swine for both meat and breeding stock.
• Several swine escaped the pen during the storm.
• Veterinarians monitor swine closely for signs of disease.
• The barn housed dozens of swine across multiple pens.
• Researchers study swine because their organs are similar in size to humans.
• A single sick animal can spread illness quickly among swine kept together.
• The county fair included a competitive swine show.
• Farmers rotate swine between pastures to manage waste and disease.
• The outbreak affected swine populations across several states.
• Historic records describe swine as common livestock even in small households.
• The agricultural fair included a dedicated pavilion for swine breeds.
• Researchers study swine partly because their physiology resembles humans closely.
• The county extension office offered classes on raising swine responsibly.
• Veterinary students study swine anatomy as part of their large-animal training.