---
title: "Index of branches of science"
chunk: 7/10
source: "https://en.wikipedia.org/wiki/Index_of_branches_of_science"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:28:12.104269+00:00"
instance: "kb-cron"
---

== O ==
Obstetrics – Medical specialty concerning pregnancy and childbirth
Oceanography – Scientific study of the ocean
Oceanology – Scientific study of the ocean
Odontology – Scientific study of teeth
Odonatology – Study of dragonflies and damselflies
Oenology – Study of wine and winemaking
Oikology – science of housekeeping 
Olfactology – study of the sense of smell
Ombrology – study of rain
Oncology – Branch of medicine dealing with, or specializing in, cancer
Oneirology – Scientific study of dreams
Onomasiology – Branch of linguistics concerned with how to express a given concept – study of nomenclature 
Onomastics – Study of proper names
Ontology – Philosophical study of being – science of pure being; the nature of things 
Oology – Branch of ornithology studying bird eggs, nests and breeding behavior
Ophiology, also known as ophidiology – Branch of herpetology that studies snakes
Ophthalmology – Field of medicine treating eye disorders
Optics – Branch of physics that studies light
Optology – study of sight 
Optometry – Field of medicine treating eye disorders – science of examining the eyes
Orbital mechanics – Field of classical mechanics concerned with the motion of spacecraft
Orchidology – Scientific study of orchids
Ornithology – Scientific study of birds
Organology – Collection of tissues with similar functionsPages displaying short descriptions of redirect targets (biology) – study of form, structure, development, and functions of plant or animal organs
Organology – Science of musical instruments and their classifications (musicology) – study of musical instruments in relation to history, culture, construction, acoustic properties and classification
Orology, also known as Mountain research – Study of mountain environments
Orthoepy – Correct pronunciation of a language 
Orthography – Set of conventions for written language 
Orthopterology – Study of grasshoppers and related insects
Oryctology – mineralogy or paleontology
Osmics – scientific study of smells
Osmology – study of smells and olfactory processes 
Osphresiology – study of the sense of smell
Osteology – Scientific study of bones
Otology – Branch of medicine for the ear
Otorhinolaryngology – Medical specialty of the head and neck