I've read somewhere that if complex is an adjective, its second syllable is stressed (com-plex), while for noun, the first one (com-plex). But e.g. this link says that adjective can also sound as noun. I also remember that my teacher (many years ago) said "com-plex object", although complex is an adjective here.

I guess stress depends on context of usage. So, what are the cases for stressing first or second syllable in adjective complex? How do I determine which syllable has to be stressed?

For example, how are "complex numbers", "complex object", "complex problem" pronounced?

  • What have you found in modern dictionaries? Commented Feb 8, 2014 at 14:15
  • I'm not familiar with the second syllable being stressed in adjectival usages. I put stress on the first syllable in all contexts. Commented Feb 8, 2014 at 14:40
  • In my speech, if complex is a noun, the stress is on the first syllable. If complex is an adjective, the primary stress is on the first syllable, but there is also secondary stress on the second syllable. So /ˈkɑm.plɪks/ for the noun and /ˈkɑmˌplɛks/ for the adjective. Commented Feb 8, 2014 at 15:12

1 Answer 1


The OED has accent on com for both noun and adjective, but accent on plex for verb. What verb, you ask. Well, it is obsolete or rare except in chemistry, where it means "form a complex with".

These hormones must complex with specific receptors in order to...

Here in America, I have heard the plex accent version on occasion. But nothing as simple as the noun/adjective distinction proposed by Ruslan.

My American dictionary has only com accent for the noun, but both possible accents for the adjective or the verb.

My advice: use accent com for the adjective, no one will object (or even notice).

Note: combined forms may accent the plex ... complexity, complexification, non-complex, super-complex.

  • 1
    I tend to stress the first syllable when I use complex attributively (Korea has a complex history) and on the second when predicatively (The history of Korea is as fascinating as it is complex); as a noun or verb, I always stress the first with a secondary stress on the second.
    – choster
    Commented Feb 8, 2014 at 16:47
  • @choster Yes. I have to agree, having listened to it that some people (definitely a minority) do put the emphasis on the 'plex'. I am sorry to have misinformed everyone. I have therefore deleted my earlier comment.
    – WS2
    Commented Feb 8, 2014 at 19:41
  • Oxford's OALD has both stress versions accepted for NAmE: oxfordlearnersdictionaries.com/definition/english/… Commented Oct 18, 2019 at 23:22

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