I do not know which of the following words is right in English: monobjective vs monoobjective. The context is scientific/formal. Example: "monoobjective optimization".

Is there any general rule in English about whether one of the two o's should be omitted in such a situation ('mono' + word starting with an unstressed 'o') or not?

Some facts:

  • There's definitely words where you drop the "o" when you add "mono" - see monorchid. – Andrey Jul 26 '15 at 14:41

I don't think the rule about the omission of 'o' before a vowel is always applied, especially in scientific names, see the list below. It mainly applies to more common and older terms such as monastery for instance.


  • One; alone; single: monocoque
  • Chemistry (Forming names of compounds) containing one atom or group of a specified kind: monoamine



  • word-forming element meaning "one, alone; containing one (atom, etc.)," from Greek mono-, comb. form of monos "single, alone," from PIE root *men- "small, isolated" (cognates: Greek manos "rare, sparse," Armenian manr "thin, slender, small," and perhaps English minnow).

( Etymonline)

List of English words prefixed with mono- in alphabetical order.

As for mono objective you can find both forms, and in the end it comes down to a matter of style and preferences:

  • A mono-objective evolutionary algorithm for Protein Structure Prediction in structural and energetic contexts

  • ... 1 time 25 0.1 hand lens, 10 times 32 0.1 stereoscopic, compound microscope, 100 times 16 0.25 monobjective, compound microscope, 250 times 8 0.50 monobjective, compound microscope, 500 times 4 0.95 limit, air-immersion objective, ...


Mono-objective seems to be the most used variant within the last few decades.

Monoobjective being the second most used.


Monobjective has been in a constant decline since roughly the 60's.


I would say monobjective looks and sounds better.

An Ngram of them both shows it is much more commonly used (or used to be 70 years ago - neither are common now):

enter image description here

Certainly other scientists have used it recently: https://hal.archives-ouvertes.fr/hal-00596142

Using monobjective and multiobjective Particle Swarm Optimization for the tuning of process control laws

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