When you write about cameras, eyes, or glasses, you'll likely type either lense or lens. Only one is correct. The standard spelling is lens, and "lense" is a misspelling. It doesn't appear in Merriam-Webster, Oxford, or any other major dictionary as a standalone word. That said, the error is extremely common, and it's not hard to see why.
Which one is correct?
Lens is the correct spelling. It refers to a curved piece of glass or other transparent material that refracts light, shaping or focusing it. The word covers camera lenses, eyeglass lenses, contact lenses, and the natural lens inside the human eye. The plural is lenses. Not "lense," and not "lenses" spelled any other way.
Use it in a sentence: "The camera's wide-angle lens distorted the edges of the image." Or: "She picked up her reading glasses from the counter and noticed one of the lenses was scratched."
Why do people write "lense"?
English creates plurals by adding an "s," which means the plural of lens becomes "lenses." When people see "lenses" often enough, they sometimes work backwards and assume the singular must end in "e." It's the same logic that produces spelling errors like "marshmellow" instead of "marshmallow": the brain fills in a letter that sounds like it belongs.
There's another nudge at work. Words like "sense," "dense," and "tense" all end in "-ense," and they follow a familiar pattern. Lens sits in the same phonetic neighbourhood, so adding an "e" feels right. It isn't.
The word "lens" comes from the Latin lens, meaning lentil, because the shape of a biconvex optical lens resembles a lentil seed. Latin borrowed directly into English without modification. No "e" was ever part of the word.
What about "lense" in technical or scientific writing?
Some people encounter "lense" in geology, where it can appear as an informal variant spelling of a geological lens (a body of rock shaped like a biconvex lens). Even there, "lens" is the preferred and more widely accepted form. If you're writing for a general audience, a photography publication, or any context involving optics or anatomy, "lens" is always the right choice. Don't rely on the rare geological variant to justify the misspelling elsewhere.
How to remember the correct spelling
One simple trick: think of the Latin lentil. Short word, no trailing "e," just four letters. L-E-N-S. The plural adds "-es" to make "lenses," which is why the word looks like it ends in "e" when it's plural. It doesn't. Strip the "-es" and you're left with "lens."
Another anchor: if you know that "dense" and "sense" are their own separate words, don't let their spelling bleed into "lens." Each word has its own history. Lens stands alone.
Quick reference
- Lens: correct. Singular noun. Example: "a camera lens," "a contact lens," "the eye's natural lens."
- Lenses: correct. Plural form. Example: "prescription lenses," "interchangeable lenses."
- Lense: incorrect. Not a standard English word. Avoid it in all contexts.
Spelling errors like this are easy to miss in a first draft. They're in the same family as confusing plain and plane: the wrong form sounds plausible, your eye slides past it, and spell-checkers don't always flag it. Slowing down to check a short word is almost always worth the two seconds it takes.
When in doubt, run a quick search in a reputable dictionary. Merriam-Webster's entry for lens lists no alternate spellings. That's your answer.