I'm not sure if this question is okay to be posted to ell.se, as I don't know if it is obvious for native speakers or not, that:

physics and mathematics both ends with '-ics', while sociology and psychology end with '-logy'.

definition from dictionary.com:

-logy: a combining form used in the names of sciences or bodies of knowledge;

-ics: a suffix of nouns that denote a body of facts, knowledge, principles, etc.

My current conclusion is that '-ics' is for subjects that involve more practical works, whereas '-logy' is for those who deal with theoretical knowledges.

But 'biology', seemingly, doesn't fit in my conclusion.

  • 2
    Since the use of -logia and -ika (which eventually turned into -logy and -ics) goes back to Ancient Greek, ELL perhaps is not the best place to ask about the differences, but I am not sure which place I'd recommend, either. Commented Aug 29, 2015 at 16:25
  • Note that cinematics, cinematology, and cinematography all seem to mean the same thing. Also note some curious pairs such as physics, physiology, phonetics, phonology, etc. Commented Aug 29, 2015 at 16:48
  • 1
    I think that is a useful observation of a general trend (also consider -nomy, which suggests quantitative study, and -graphy, which suggests writing and recording), but many subject names are historical choices and do not really fit into the patterns. (Additional "curious pairs": astrology / astronomy; ecology / economy / economics)
    – Wim Lewis
    Commented Aug 29, 2015 at 19:14
  • I think this is a good question for ELU.
    – Dog Lover
    Commented Aug 30, 2015 at 7:01
  • @DogLover Maybe you could flag it for migration.
    – user230
    Commented Sep 30, 2015 at 7:47

3 Answers 3


When discussing this question, you might find it helpful to search for lists of academic disciplines and fields of knowledge. For example, Wikipedia has a nice list.


One of the problems with this situation is that English simply does not have rules addressing what you seek to (empirically) define.

English is wrought with so many exceptions that the only way to understand the correct form is through experience.


There is no system in the names of scientific disciplines and it is futile to try to find a system.

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