Quick answer: An ordinance is an authoritative order or rule, especially a law passed by a local or municipal authority: The city passed a new ordinance banning noise after 10pm. Ordnance refers to military weapons, ammunition, and related equipment: The area was cleared of unexploded ordnance. The words are unrelated in meaning despite differing by a single letter. For a fuller definition, see the Cambridge Dictionary entry for ‘ordinance’.
Comparison Table
| Word | Part of Speech | Meaning | Example |
|---|---|---|---|
| ordinance | noun | an authoritative order or rule, especially a municipal or local law | a city ordinance regulating parking |
| ordnance | noun | military weapons, ammunition, and related equipment | the ordnance depot supplying the base |
Using Ordinance
An ordinance is a formal rule, decree, or piece of legislation, usually issued by a local council, municipality, or religious authority.
The town council introduced a new ordinance restricting parking on Main Street.
Building work must comply with local ordinances.
Historically, church ordinances governed many aspects of community life.
The mayor signed the ordinance into effect immediately.
Using Ordnance
Ordnance is a specialised term for military supplies, particularly weapons, ammunition, and combat equipment, and is common in military and historical contexts.
The demolition team was called to defuse unexploded ordnance.
The fort's ordnance included several large cannons.
Military ordnance was transported under heavy guard.
The Ordnance Survey originally mapped Britain for military purposes.
Memory Trick
OrdInance has an "I" like "law" — think of a local ordinance as an official instruction. OrdnAnce has no "I" — think of it starting like "armaments", related to weapons.
Common Mistakes
✗ The council passed a new ordnance about waste disposal.
✓ The council passed a new ordinance about waste disposal.
✗ Soldiers loaded the ordinance onto the truck.
✓ Soldiers loaded the ordnance onto the truck.
Tips to Avoid Confusion
- Ask: is this about a law, rule, or decree? Use ordinance.
- Ask: is this about military weapons or equipment? Use ordnance.
- Remember "Ordnance Survey", the UK's national mapping agency, historically linked to military surveying.
- If you can substitute the word "law" or "decree", the correct spelling is ordinance.
For more on related grammar, see nouns. Also confusing: Assent vs Ascent, Allowed vs Aloud, Altar vs Alter. Browse all confusing word pairs →
Quick Check: Ordinance or Ordnance?
4 fill-in-the-blank questions — choose the correct word for each sentence.
1. “The city introduced a new noise ___ last month.” (a law)
2. “Bomb disposal teams removed the unexploded ___.” (weapons)
3. “The museum has a display of historic ___ used in the war.”
4. “All new buildings must follow the local ___.”
Frequently Asked Questions
What is the difference between ordinance and ordnance?
Ordinance means an authoritative order or rule, especially a municipal law: "a city ordinance banning noise after 10pm." Ordnance refers to military weapons, ammunition, and equipment: "unexploded ordnance." The words differ by a single letter but are completely unrelated in meaning.
Where is ordinance most commonly used?
Ordinance is most common in local government and legal contexts, particularly in American English, where cities and municipalities pass ordinances governing things like zoning, noise, parking, and public safety.
Where is ordnance most commonly used?
Ordnance is most common in military, historical, and news contexts, referring to weapons, ammunition, or explosive devices: "an ordnance disposal unit", "unexploded ordnance from the war."
What is the Ordnance Survey?
The Ordnance Survey is the UK's national mapping agency, originally established for military purposes (hence the name 'ordnance') to produce accurate maps for defence and artillery planning. Today it produces detailed maps for public and commercial use.
Is 'ordinance' related to the word 'order'?
Yes — ordinance comes from the same Latin root as 'order' and 'ordain', reflecting its meaning of an official rule or decree issued by an authority.
Is 'ordnance' related to the word 'ordain' as well?
Historically, yes, both ordinance and ordnance derive from the same Old French root related to arranging or ordaining, but ordnance narrowed over time to specifically mean military equipment, particularly artillery and munitions.
What does 'unexploded ordnance' mean?
Unexploded ordnance (often abbreviated UXO) refers to bombs, shells, grenades, or other munitions that failed to detonate when deployed and remain dangerous, requiring specialist disposal, especially in former conflict zones.
Can 'ordinance' refer to a religious rule?
Yes, in some traditions, particularly certain Christian denominations, 'ordinance' can refer to a religious rite or practice prescribed by the church, such as baptism or communion, treated as an authoritative religious observance.
Why are these two words so often confused?
They are pronounced almost identically and differ by only one letter (i versus no i in the second syllable), yet their meanings — civil law versus military hardware — are entirely unrelated, making them a classic spelling trap.
How can I remember ordinance vs ordnance?
Ordinance has an extra 'i', just like the word 'law' has an 'a' for authority — link the longer spelling to legal rules. Ordnance is shorter, just like 'arms' — link the shorter spelling to weapons and the military.