Lifetime is the correct spelling in almost every situation you’ll encounter. It’s one word, no space, and it works as a single noun meaning “the duration of someone’s life” or “the entire period something exists.” The two-word version, “life time,” is essentially never correct in standard English — you’ll rarely if ever need it.
The Short Answer
Write it as one word: lifetime. This holds true whether you’re talking about a person’s lifespan, a product’s lifetime warranty, or “the opportunity of a lifetime.” English merged “life” and “time” into a single compound noun decades ago, and dictionaries only list it that way.
“Life time” as two separate words isn’t recognized by Merriam-Webster, Oxford, or Cambridge dictionaries. If you see it written that way, it’s almost always a typo or a case where “life” and “time” happen to sit next to each other for a different grammatical reason — not the same word at all.
Quick Reference
| Form | Correct? | Notes |
|---|---|---|
| lifetime | Yes | Standard, one word, always safe |
| life time | No | Not a recognized compound noun |
| life-time | No | Hyphenated form is outdated and rarely used today |
Why People Get It Wrong
The confusion happens because “life” and “time” are both common, standalone words. Your brain sees two familiar words and assumes they should stay separate, the way you’d write “life goal” or “life story.” But “lifetime” behaves differently — it fused into a true compound noun long ago, similar to how “however” or “nevertheless” started as two words and became one.
Autocorrect and spell-check tools reinforce the habit of second-guessing yourself, but here the rule is simple and doesn’t have layers of exceptions like some spelling questions do.
Examples in a Sentence
- She spent her entire lifetime in the same small town.
- This blender comes with a lifetime warranty.
- Winning that scholarship was the chance of a lifetime.
- The company’s average customer lifetime value has doubled.
- He said it was a once-in-a-lifetime trip.
The One Exception
There’s a narrow case where “life” and “time” sit next to each other as separate words, but they’re not functioning as the compound noun “lifetime” — they’re just two words that happen to be adjacent, usually with something implied between them or in a different grammatical role. For example: “In his life, time seemed to move slower.” Here “life” ends one clause and “time” begins the next thought. This isn’t really “life time” as a unit — it’s coincidental proximity, and it’s rare enough that you don’t need to worry about it in everyday writing.
Which to Use When
- Talking about a person’s life span: use lifetime (“a once-in-a-lifetime event”).
- Warranties, guarantees, or product durability: use lifetime (“lifetime membership”).
- Business or analytics terms: use lifetime (“customer lifetime value,” “lifetime earnings”).
- Never default to “life time” as two words — there’s no context where that spelling is standard.
Key Takeaways
- Lifetime is always one word — this is the only standard spelling.
- “Life time” as two words is not recognized in any major dictionary.
- The old hyphenated form “life-time” is outdated and shouldn’t be used in modern writing.
- Common phrases like “lifetime warranty,” “once in a lifetime,” and “lifetime value” all use the single-word form.
Frequently Asked Questions
Is “lifetime” one word or two words?
It’s one word. “Lifetime” is a standard compound noun, and writing it as “life time” is considered incorrect in modern English.
Is “life-time” with a hyphen ever correct?
It appeared in older texts, but it’s outdated now. Modern style guides and dictionaries use the closed, one-word form “lifetime” without a hyphen.
What does “lifetime” mean?
It means the length of time someone is alive, or the entire period during which something exists, functions, or remains valid — as in a “lifetime warranty.”
How do I use “lifetime” in a sentence correctly?
Use it as a single noun or adjective: “This is a once-in-a-lifetime opportunity” or “The device has a ten-year lifetime.” Avoid splitting it into “life time.”
Why does spell-check sometimes flag “lifetime”?
It usually doesn’t — “lifetime” is standard. If your spell-check flags it, double-check you haven’t accidentally typed “life time” or “life-time” instead.
Spelling questions like this one are quick to answer but easy to second-guess in the moment. If a similar word pair has been tripping you up, take a look around the site — chances are it’s already covered.
