This list includes 57 Simple words that start with O, from “oak” to “oxen”. Most are short, high-frequency words useful for teachers, parents, and early learners.

Simple words that start with O are common, everyday words beginning with the letter O, often learned early. For example, “oak” names a familiar tree while “oxen” shows an older plural still used in English.

Below you’ll find the table with [COLUMN_NAMES].

Word: The simple O word itself, shown so you can scan and choose terms for teaching or writing.

Definition: A concise, learner-friendly definition so you quickly grasp each word’s basic meaning and classroom use.

Etymology: One-line origin that shows the word’s language roots and gives cultural or historical context.

Part of speech: The grammatical role (noun, verb, adjective) so you can use the word correctly in sentences.

Notes: Practical tips, common variants, or frequency markers to help you pick words for lessons or lists.

Simple words that start with O

Word Part of speech Syllables Origin Description
of preposition 1 Old English Shows belonging or part of something; very common short preposition.
on preposition 1 Old English Indicates position in contact with or supported by a surface.
or conjunction 1 Old English Connects choices or alternatives between words or ideas.
one pronoun 1 Old English The number 1 or a single person or thing.
once adverb 1 Old English One time; something that happened a single time.
only adverb 2 Old English Means solely or no one/thing else.
open verb 2 Old English To move something so it is not closed; also an adjective.
out adverb 1 Old English Away from the inside; outside or not in.
our pronoun 1 Old English Belonging to us; the possessive form of we.
over preposition 2 Old English Above or across; also used in many common phrases.
old adjective 1 Old English Having lived or existed for many years.
off adverb 1 Old English Away from a place or removed; opposite of on.
own verb 1 Old English To possess something; can also describe possession.
other adjective 2 Old English Different or remaining person or thing.
order noun 2 Latin via Old French Instruction, arrangement, or sequence of things.
oh interjection 1 Old English Expresses surprise, attention, or a reaction.
okay interjection 2 American English Casual yes or agreement; very common in speech.
oil noun 1 Old English Fatty liquid used for cooking, fuel, or lubrication.
owl noun 1 Old English Nocturnal bird with big eyes, often in children’s stories.
ox noun 1 Old English A large domesticated bovine often used for work.
odd adjective 1 Old English Strange or unusual; also used for odd numbers.
oven noun 2 Old English Enclosed space for baking or cooking food.
oar noun 1 Old English Long pole used to row a boat.
owe verb 1 Old English To need to pay or give something to someone.
ocean noun 2 Greek via Latin A very large body of salt water; the sea.
octopus noun 3 Greek A sea animal with eight arms; common in children’s books.
orange noun 2 Old French A fruit and a color; common everyday word.
ounce noun 1 Old French A small unit of weight often used in recipes.
orca noun 2 Latin A large toothed whale also called a killer whale.
olive noun 2 Latin via Old French Small fruit used for food and oil.
oval adjective 2 Latin via Old French Shaped like an egg; rounded but longer.
obvious adjective 3 Latin via Old French Easy to see or understand.
obey verb 2 Old French To follow rules or do what someone asks.
orbit noun 2 Latin The path one object takes around another, like a planet.
organ noun 2 Latin A body part or musical instrument; common word.
origin noun 3 Latin Where something begins or comes from.
oxen noun 2 Old English Plural of ox; two or more working bovines.
oasis noun 3 Greek A green spot with water in a desert.
omit verb 2 Latin To leave something out or skip it.
opt verb 1 Latin To choose one thing over others.
opposite adjective 3 Latin via Old French Completely different or on the other side.
ouch interjection 1 Old English Short exclamation used when in pain.
opera noun 3 Latin A musical drama performed with singing.
opinion noun 3 Latin via Old French A person’s thought or belief about something.
orphan noun 2 Greek via Latin A child whose parents have died.
output noun 2 English What comes out of a process or machine.
outside adverb 2 Old English On or to the outer side; not inside.
oust verb 1 Old French To drive out or remove from a position or place.
oat noun 1 Old English A cereal grain used for porridge and animal feed.
oak noun 1 Old English A large sturdy tree with acorns.
ogre noun 2 French A mythical monster often found in fairy tales.
odor noun 2 Latin via Old French A smell, pleasant or unpleasant.
ow interjection 1 Old English Short cry of pain, common with young children.
ore noun 1 Old English Rock that contains metal that can be mined.
ours pronoun 1 Old English The form of ours showing possession by us.
onto preposition 2 Old English Moving to be on the surface of something.
once adverb 1 Old English (Duplicate avoided) use earlier entry for definition.

Descriptions

of
on
or
one
once
only
open
out
our
over
old
off
own
other
order
oh
okay
oil
owl
ox
odd
oven
oar
owe
ocean
octopus
orange
ounce
orca
olive
oval
obvious
obey
orbit
organ
origin
oxen
oasis
omit
opt
opposite
ouch
opera
opinion
orphan
output
outside
oust
oat
oak
ogre
odor
ow
ore
ours
onto
once
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