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?


3 Answers 3


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

  • 3
    The ngrams for life cycle,lifecycle,life-cycle,life - cycle is more informative, showing that life-cycle is used much more than lifecycle. May 21, 2012 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, 2012 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. May 22, 2012 at 0:23
  • I’m thinking that your ngram may be wrong; please consider this.
    – tchrist
    Dec 13, 2012 at 14:21
  • 1
    @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, 2012 at 5:43

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.

  • 1
    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, 2021 at 8:21

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.

  • 2
    Can you give an example of the term used referring to a single concept?
    – joedragons
    Mar 24, 2015 at 14:59
  • 2
    @joedragons: I guess its use in product lifecylce management might be an example. (I am not a native speaker). Nov 5, 2021 at 8:54

Not the answer you're looking for? Browse other questions tagged or ask your own question.