“ordinance” vs. “ordnance”
Write "ordinance" for a local law or official regulation; write "ordnance" for military weapons, ammunition, or supply.
ordinance
"Ordinance" is a noun naming an authoritative rule or law, typically issued by a local government or municipal authority ("a city ordinance banning open fires"). It comes from Old French "ordenance," from Latin "ordinare" (to arrange, to put in order), the same root that gives English "order" and "ordain," reflecting the word's core sense of establishing proper order through official rule.
ordnance
"Ordnance" is a noun naming military weapons and supplies collectively, especially large weapons, ammunition, and explosives ("unexploded ordnance"), and historically the branch of an army or government responsible for supplying weapons and munitions. It comes from a contraction of "ordinance" itself, historically the same word, which split off in the 15th and 16th centuries into a separate spelling specifically for military weaponry and supply, dropping the middle "i" along the way.
The real distinction
"Ordinance" and "ordnance" are historically the same word, a rare case on this list where the confusion comes from a genuine, documented split in spelling rather than two unrelated words converging by accident, similar to the metal/mettle pair elsewhere. Over centuries, "ordinance" kept its full spelling and its meaning of an official rule or law, while "ordnance" dropped the middle "i" and narrowed specifically to mean military weapons and supplies, likely influenced by the closely related word "ordnance store" or "ordnance department," military terms that solidified the shorter spelling within that specific field. Today the two spellings are firmly distinct in meaning and not interchangeable: "ordinance" belongs to municipal law and local government writing (zoning ordinances, noise ordinances, building ordinances), while "ordnance" belongs to military, defense, and munitions writing (unexploded ordnance, ordnance depot, artillery ordnance). If the sentence concerns a local law, rule, or regulation, you want "ordinance"; if the sentence concerns weapons, ammunition, or military supply, you want "ordnance." Because both words are relatively formal, appearing mostly in legal, governmental, or military writing rather than casual conversation, this is a pair that many everyday writers rarely need at all, but professionals in city government, urban planning, defense, or military history need to get right consistently and reliably. City planning documents frequently reference specific ordinance numbers when citing local law (as in 'Ordinance 2024-15'), a formal citation practice unique to municipal governance that has no equivalent in ordnance-related military or defense writing. Historically, both words descend from the same root, but the split became especially entrenched once each term developed its own dedicated professional field around it — municipal law for 'ordinance,' military logistics for 'ordnance' — meaning that today a writer working in one field rarely if ever needs the other word at all, reducing the practical risk of confusion primarily to writers unfamiliar with either specialized vocabulary.
Examples with “ordinance”
- The city passed a new noise ordinance last month.
- Local ordinances restrict how tall fences can be.
- The council debated the proposed zoning ordinance for hours.
- An old ordinance still bans parking on that street overnight.
- The building violated several fire-safety ordinances.
- Residents petitioned against the controversial leash ordinance.
- The town updated its recycling ordinance this year.
- A new ordinance requires permits for backyard fires.
Examples with “ordnance”
- Crews carefully removed unexploded ordnance from the old battlefield.
- The base stores its ordnance in a secured, separate facility.
- Military ordnance was shipped ahead of the planned exercise.
- The museum displays retired ordnance from both world wars.
- Engineers were called in to defuse the buried ordnance.
- The convoy transported ordnance under heavy security.
- Decades-old ordnance still occasionally surfaces in former conflict zones.
- The depot handles storage and transport of heavy ordnance.
Memory trick
Remember "ordinance" keeps its full middle "i," matching "order" and "ordain," its close relatives in meaning about rules and arrangement. "Ordnance" drops that "i" entirely, a visual shortening that mirrors how the military sense split off from the original word — think "no i in ordnance" as a quick spelling check tied to weapons and supply.