on

UK: /ˈɒn/ US: /ɑn, ɔn/ ,'on': (on, ôn); 'On': (Bible on)

WordReference Random House Learner's Dictionary of American English © 2025

on /ɑn, ɔn/   prep. 

1. so as to be or to remain supported by:
   Put the package on the table.
2. so as to be attached to or unified with:
   There is a label on the jar.
3. so as to be a covering or wrapping for:
   Put the blanket on the baby.
4. in connection, association, or cooperation with:
   to serve on a jury.
5. so as to be a supporting part or base of:
   legs on a chair.
6. (used to show that the preceding noun has the following noun as its place, location, situation, etc.):
   an ugly scar on the face.
7. very close to;
   at the edge of:
   a house on the lake.
8. in the direction of:
   to sail on a southerly course.
9. using as a means of carrying or of supporting or providing movement:
   arrived on the noon plane.
10. by the agency or means of:
    drunk on wine.
11. directed against or toward:
    She played a joke on him.
12. having as a subject;
    being about (something):
    a new book on dogs.
13. in a state, condition, or process of:
    The workers are on strike.
14. engaged in or involved with:
    I'm on the second chapter of the book.
15. subject to:
    If there is a doctor on call it means that a doctor can be summoned quickly in an emergency.
16. having as a source or agent:
    He came to depend on his friends.
17. having as a basis or ground:
    on my word of honor.
18. assigned to or working at:
    Who's on duty today?
19. (used with days and dates) at the time mentioned:
    The train arrives every hour on the hour (= at one, two, three o'clock, etc.)
20. at the time or occasion of:
    You have to pay cash on delivery (= at the time delivery is made).
21. within the required limits of:
    The train arrived on time.
22. having as the object or end of motion:
    The demonstrators marched on the capital.
23. having as the object or the goal of action, thought, desire, etc.:
    to gaze on a scene.
24. having as the subject or reference;
    with respect to:
    What are your views on rock music?
25. Informal Terms paid for by, esp. as a treat or gift:
    Dinner is on me.
26. taking or using as a measure or cure to improve one's health, energy, etc.:
    He's on a low-salt diet.
27. regularly taking or addicted to:
    She's not on drugs anymore.
28. Informal Terms with;
    carried by:
    I have no money on me.
29. so as to disturb or affect in a bad way:
    My hair dryer broke on me.
30. having as a risk or unfortunate result:
    on pain of death.
31. in addition to:
    millions on millions of stars.

adv. 

32. in, into, or onto a position of being supported or attached:
    Sew the buttons on.
33. in, into, or onto a position of covering or wrapping:
    Put your raincoat on.
34. tightly attached to a thing, such as for support:
    Hold on!
35. toward a place, point, activity, or object:
    to look on while others work.
36. forward, onward, or along, such as in any course or process later on:
    further on.
37. with continuous activity:
    continued on with his job.
38. into or in active operation or performance:
    Turn the gas on.

adj. [be + ~]

39. operating or in use:
    Is the radio on?
40. taking place;
    occurring:
    Don't you know there's a war on?
41. being broadcast:
    What's on tonight, anything interesting to watch?
42. scheduled or planned:
    Do you have anything on for tomorrow?
43. Informal Terms
    • behaving in a very animated or theatrical manner:
      He never stops and just relaxes; he's always on.
    • functioning or performing at one's best:
      The pitcher is really on today.

Idioms

44. Idioms on and off, with periods of time in between;
    intermittently.
45. Idioms on and on, at great length:
    to chatter on and on.
    Compareat, in.

Usage

See about.

WordReference Random House Unabridged Dictionary of American English © 2025

on  (on, ôn), prep. 

1. so as to be or remain supported by or suspended from:
   Put your package down on the table; Hang your coat on the hook.
2. so as to be attached to or unified with:
   Hang the picture on the wall. Paste the label on the package.
3. so as to be a covering or wrapping for:
   Put the blanket on the baby. Put aluminum foil on the lamb chops before freezing them.
4. in connection, association, or cooperation with;
   as a part or element of:
   to serve on a jury.
5. so as to be a supporting part, base, backing, etc., of:
   a painting on canvas;
   mounted on cardboard;
   legs on a chair.
6. (used to indicate place, location, situation, etc.):
   a scar on the face;
   the book on the table;
   a house on 19th Street.
7. (used to indicate immediate proximity):
   a house on the lake; to border on absurdity.
8. in the direction of:
   on the left; to sail on a southerly course.
9. (used to indicate a means of conveyance or a means of supporting or supplying movement):
   on the wing; This car runs on electricity. Can you walk on your hands? I'll be there on the noon plane.
10. by the agency or means of:
    drunk on wine;
    talking on the phone;
    I saw it on television.
11. in addition to:
    millions on millions of stars.
12. with respect or regard to (used to indicate the object of an action directed against or toward):
    Let's play a joke on him. Write a critical essay on Shakespeare.
13. in a state or condition of;
    in the process of:
    on strike; The house is on fire!
14. subject to:
    a doctor on call.
15. engaged in or involved with:
    He's on the second chapter now.
16. (used to indicate a source or a person or thing that serves as a source or agent):
    a duty on imported goods; She depends on her friends for encouragement.
17. (used to indicate a basis or ground):
    on my word of honor; The movie is based on the book.
18. (used to indicate risk or liability):
    on pain of death.
19. (used to indicate progress toward or completion of an objective):
    We completed the project on budget.
20. assigned to or occupied with;
    operating:
    Who's on the switchboard this afternoon?
21. [Informal.] so as to disturb or affect adversely:
    My hair dryer broke on me.
22. Informal Terms paid for by, esp. as a treat or gift:
    Dinner is on me.
23. taking or using as a prescribed measure, cure, or the like:
    The doctor had her on a low-salt diet.
24. regularly taking or addicted to:
    He was on drugs for two years.
25. Informal Terms with;
    carried by:
    I have no money on me.
26. (used to indicate time or occasion):
    on Sunday; We demand cash on delivery.
27. (used to indicate the object or end of motion):
    to march on the capital.
28. (used to indicate the object or end of action, thought, desire, etc.):
    to gaze on a scene.
29. (used to indicate subject, reference, or respect):
    views on public matters.
30. (used to indicate an encounter):
    The pickpocket crept up on a victim.
31. on the bow, [Naut.] bow³ (def. 7).

adv. 

32. in, into, or onto a position of being supported or attached:
    Sew the buttons on.
33. in, into, or onto a position of covering or wrapping:
    Put your raincoat on.
34. fast to a thing, as for support:
    Hold on!
35. toward a place, point, activity, or object:
    to look on while others work.
36. forward, onward, or along, as in any course or process:
    further on.
37. with continuous activity:
    to work on.
38. into or in active operation or performance:
    Turn the gas on.
39. Idioms on and off, off (def. 22a).
40. Idioms on and on, at great length, so as to become tiresome:
    They rambled on and on about their grandchildren.

adj. 

41. operating or in use:
    The television set was on. Is your brake on?
42. taking place;
    occurring:
    Don't you know there's a war on?
43. performing or broadcasting:
    The radio announcer told us we were on.
44. Informal Terms
    • behaving in a theatrical, lively, or ingratiating way:
      Around close friends, one doesn't have to be on every minute.
    • functioning or performing at one's best:
      When she's on, no other tennis player is half as good.
45. scheduled or planned:
    Anything on after supper?
46. Sport [Baseball.] positioned on a base or bases:
    They had two men on when he hit the home run.
47. Sport [Cricket.] noting that side of the wicket, or of the field, on which the batsman stands.
48. Idioms on to, aware of the true nature, motive, or meaning of:
    I'm on to your little game.

n. 

49. Sport [Cricket.] the on side.

• bef. 900; Middle English on, an, Old English: on, in, to; cognate with Dutch aan, German an, Old Norse ā, Gothic ana; akin to Greek aná up, upon (see ana-)

On  (on), n. 

1. Bible, Place Names Biblical name of Heliopolis. 

ON, 

1. Language Varieties Old Norse.
Also, ON., O.N. 
2. Abbreviations Ontario, Canada (approved for postal use).

-on¹ ,

1. Physics a suffix used in the names of subatomic particles (gluon;
   meson;
   neutron), quanta (graviton), and other minimal entities or components (cistron;
   codon;
   magneton;
   photon).

• compare proton probably extracted from ion

-on² ,

1. Chemistry a suffix used in the naming of inert gaseous elements:
   neon.

• Greek -on, neuter of -os adjective, adjectival ending

Collins Concise English Dictionary © HarperCollins Publishers::

on / ɒn/ preposition

1. in contact or connection with the surface of; at the upper surface of: an apple on the ground, a mark on the table cloth
2. attached to: a puppet on a string
3. carried with: I've no money on me
4. in the immediate vicinity of; close to or along the side of: a house on the sea, this verges on the ridiculous!
5. within the time limits of a day or date: we arrived on Thursday
6. being performed upon or relayed through the medium of: what's on television?
7. at the occasion of: on my retirement
8. used to indicate support, subsistence, contingency, etc: they live on bread, it depends on what you want
9. regularly taking (a drug): she's on the pill
10. addicted to: he's on heroin
11. by means of (something considered as a mode of transport) (esp in such phrases as on foot, on wheels, on horseback, etc)
12. in the process or course of: on a journey, on strike
13. concerned with or relating to: a tax on potatoes, a programme on archaeology
14. used to indicate the basis, grounds, or cause, as of a statement or action: I have it on good authority
15. against: used to indicate opposition: they marched on the city at dawn
16. used to indicate a meeting or encounter: he crept up on her
17. (used with an adjective preceded by the) indicating the manner or way in which an action is carried out: on the sly, on the cheap
18. staked or wagered as a bet: ten pounds on that horse
19. charged to: the drinks are on me

adverb (often used as a particle)

1. in the position or state required for the commencement or sustained continuation, as of a mechanical operation: the radio's been on all night
2. attached to, surrounding, or placed in contact with something
3. in a manner indicating continuity, persistence, concentration, etc: don't keep on about it, the play went on all afternoon
4. in a direction towards something, esp forwards; so as to make progress: we drove on towards Lagos, march on!
5. on and off, off and on ⇒ intermittently; from time to time
6. on and on ⇒ without ceasing; continually

adjective

1. functioning; operating: turn the switch to the on position
2. (postpositive) performing, as on stage: I'm on in five minutes
3. definitely taking place: the match is on for Friday, their marriage is still on
4. tolerable, practicable, acceptable, etc: your plan just isn't on
5. on at ⇒ nagging: I was always on at her to go to the doctor
6. (of a bowler) bowling

noun

1. (modifier) relating to or denoting the leg side of a cricket field or pitch: the on side, an on drive
2. (in combination) used to designate certain fielding positions on the leg side: long-on, mid-on

Etymology: Old English an, on; related to Old Saxon an, Old High German, Gothic ana

WordReference Random House Unabridged Dictionary of American English © 2025

ON, +

1. Abbreviations Ontario, Canada (approved for postal use).

Collins Concise English Dictionary © HarperCollins Publishers::

ON abbreviation

1. Old Norse
2. (esp in postal addresses) Ontario

Collins Concise English Dictionary © HarperCollins Publishers::

On / ɒn/ noun

1. the ancient Egyptian and biblical name for Heliopolis

Collins Concise English Dictionary © HarperCollins Publishers::

-on suffix:forming_nouns

1. indicating a chemical substance: interferon, parathion
2. (in physics) indicating an elementary particle or quantum: electron, photon
3. (in chemistry) indicating an inert gas: neon, radon
4. (in biochemistry) a molecular unit: codon, operon

Etymology: from ion