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I notice great variability in how this concept is expressed. Does the term vary depending on the context? Should one use one variation when discussing biology, for example, and another when talking about product phases? Wikipedia uses different forms in way that seems random. So, too, does the New York Times, based on basic search. An earlier discussion of the variations in connection with technology notes that "A compound generally starts open (life cycle), migrates to hyphenated (life-cycle), and ends up closed (lifecycle)." Are we at the closed stage for the term in a general sense?

Bill Lefurgy
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3 Answers3

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My medical dictionaries (Dorland's Illustrated, 30th Ed.; Saunders Comprehensive Veterinary Dictionary) either list it as two words (Dorland's) or not at all (Saunders). So I would say in medical literature fields, where the context would be something like the life cycle of a parasite, it's still two words.

And I'm not sure that lifecycle and life-cycle are nearly as common as life cycle. Here's the NGram for life cycle vs. lifecycle vs. life-cycle. enter image description here

JLG
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    The ngrams for life cycle,lifecycle,life-cycle,life - cycle is more informative, showing that life-cycle is used much more than lifecycle. – James Waldby - jwpat7 May 21 '12 at 18:10
  • @jwpat7, what would adding the space around the hyphen indicate? I'm not understanding the point. What results would that "catch"? – JLG May 21 '12 at 19:17
  • My understanding is that in ngrams search string life-cycle does not match anything, while search string life - cycle matches the string life-cycle. – James Waldby - jwpat7 May 22 '12 at 00:23
  • I’m thinking that your ngram may be wrong; please consider this. – tchrist Dec 13 '12 at 14:21
  • @tchrist, It may be, but when I look at your link it says "Note: the Ngram Viewer treats quotation marks literally." How do you know that you're searching for life-cycle with life "-" cycle? Is that how you're supposed to search for hyphenated words? – JLG Dec 14 '12 at 01:11
  • @JLG That is is my suspicion, yes. Notice how it doesn’t flat-line now. – tchrist Dec 14 '12 at 03:47
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    @tchrist, I don't think that's right. When you search for just life "-" cycle, and you look at what's found, it's not hyphenated life-cycle. It's the separate words life and cycle that are found. Look at the works it find its in below the graph. – JLG Dec 14 '12 at 05:43
  • +1 Fact-based answer of incredible quality. Thank you. –  May 18 '14 at 09:01
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Four online dictionaries I consulted (Merriam-Webster, Oxford Dictionaries, Macmillan, and Dictionary.com) all agree on the open form life cycle.

In particular, the Dictionary.com definition in the link uses the open form for all the senses life cycle.

Gnawme
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    Language rules change depending on real usage. In Google Search you get 60M of usages for "lifecycle", 102M for "life-cycle" and 113M for "life cycle". – Zon Aug 12 '21 at 08:21
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My feeling is that if referring to a single concept, it should be a single or closed word, i.e. lifecycle.

On the other hand, when referring to separate concepts, the open usage would be more appropriate. For example, the various stages of an insect's life would be referred to as a life cycle.

It eventually comes down to context and that is the responsiblity of the individual writer/author/editor, etc.

RegDwigнt
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Ivan W
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