Wide is an adjective describing something — "The door is 90 cm wide", "a wide river". Width is the noun for the measurement itself — "the width of the door", "measure the width first". They express the same idea; only their grammar differs, so the choice depends on the slot in your sentence, not on your meaning.
The core difference
This is a grammar pairing rather than a meaning pairing. English builds these adjective–noun couples all over the place: long/length, deep/depth, high/height, strong/strength, broad/breadth. Wide and width work exactly the same way, and once you see the pattern you can apply it to all of them.
How to use wide
Wide describes a thing. It sits either before a noun or after a linking verb such as is, seems or became:
- "They knocked through to make a wide opening."
- "The shelf is 60 centimetres wide."
- "The gap between the two figures is uncomfortably wide."
Note the second example. When a measurement comes first, English puts the adjective last: three metres wide, never "three metres width".
How to use width
Width names the quantity, so it behaves like any noun — it takes the, a or its, and it can be a subject or an object:
- "Check the width of the doorway before ordering."
- "The width has been reduced to allow for insulation."
- "These shoes come in three widths."
The test
Look at what comes immediately before the word. If it is the, a, its, this or a possessive, you need the noun: width. If it follows a form of be or a number-plus-unit, or sits directly in front of a noun, you need the adjective: wide. A quick swap also works — try substituting length and long. Whichever of those two fits, take the matching member of this pair.
The edge cases
Wide doubles as an adverb, which is where learners often hesitate: "Open wide", "The door was flung wide", "His shot went wide of the post." There is also widely, which means "over a broad range" rather than "by a large distance" — "widely read", "opinions vary widely". Do not use widely for physical spread: it is "the doors slid wide open", not "widely open".
One more pitfall: wide and broad overlap but are not always swappable. Physical measurements take wide (a two-metre-wide path); figurative range often prefers broad (broad agreement, a broad range of views, broad shoulders). "Wide range" is also completely standard, so this one is a matter of collocation rather than rule.
