Online vs. On-Line: What’s The Difference?

If you have ever seen the word of the day “online” spelled as on-line, you might have found yourself confused about the spelling. How could it be that you have seen a word so often but then second guess yourself, did you just forget or is it just the English language being as complicated as ever with words constantly evolving. 

Your writing, at its best

Compose bold, clear, mistake-free, writing with Grammarly's AI-powered writing assistant

What Is the Definition of the Words Online and On-Line?

According to Merriam-Webster dictionary, the word online is an adverb and is defined as:

  • operating under the direct control of, or connected to, a main computer.
  • connected by computer to one or more other computers or networks, as through a commercial electronic information service or the internet.
  • of or denoting a business that transmits electronic information over telecommunications lines:
    • an online bookstore.
  • available or operating on a computer or computer network:
    • an online dictionary.
  • by means of or using a computer:
    • online shopping.
  • Radio. (of a network) supplying affiliated stations with all or a substantial part of their programming.
  • Television. of or relating to the final editing of a videotaped program.
  • done or accomplished while in operation or active service:
    • online maintenance.
  • located on major routes or rail lines:
    • online industries.
  • with or through a computer, especially over a network.

What Is the Difference Between Online and On-line?

As time passes by, words evolve and change meaning. Words are adapted to fit with the times and get new meanings and new spellings. The word on-line originally was used to refer to a train being on its rails. This was used back in 1915 and it wasn’t till 1945 that it started to see other uses. 

As it changed and the internet was invented it shifted slowly from the hyphenated version on-line to online. In the 90’s it was still common to refer to the internet with the compound word on-line. There are still some uses today but the far more common spelling is online as a single word in the English usage. 

Synonyms of Online and On-Line

  • Wired 
    • equipped with wires, as for electricity or telephone service.
    • made of wire; consisting of or constructed with wires:
    • a wired barrier.
    • tied or secured with wires:
    • wired bales of wastepaper.
    • strengthened or supported with wires:
    • a sculpture of wired papier-mâché.
    • Slang. tense with excitement or anticipation; edgy.
    • equipped so as to receive cable television.
  • Networked
    • any netlike combination of filaments, lines, veins, passages, or the like:
      • a network of arteries; a network of sewers under the city.
    • Radio and Television.
      • a group of transmitting stations linked by wire or microwave relay so that the same program can be broadcast or telecast by all.
      • a company or organization that provides programs to be broadcast over these stations:
      • She was hired by the network as program coordinator.
    • Telecommunications, Computers. a system containing any combination of computers, computer terminals, printers, audio or visual display devices, or telephones interconnected by telecommunication equipment or cables: used to transmit or receive information.
    • an association of individuals having a common interest, formed to provide mutual assistance, helpful information, or the like:
      • a network of recent college graduates.
    • a system of interrelated buildings, offices, stations, etc., especially over a large area or throughout a country, territory, region, etc.:
    • a network of supply depots.
    • Electricity. an arrangement of conducting elements, as resistors, capacitors, or inductors, connected by conducting wire.
  • Accessible
    • easy to approach, reach, enter, speak with, or use.
    • able to be used, entered, reached, etc.:
      • an accessible road; accessible Mayan ruins.
    • suitable for disabled people to reach, enter, or use, as a result of design modifications:
      • wheelchair-accessible vans;
    • modified controllers to make video games accessible.
    • readily understandable:
    • Students may believe that poetry is not accessible because of its metaphorical language.
    • obtainable; attainable:
    • accessible evidence.
    • open to the influence of (usually followed by to):
    • accessible to bribery.
  • Connected
    • united, joined, or linked.
    • having a connection.
    • joined together in sequence; linked coherently:
      • connected ideas.
    • related by family ties.
    • having social or professional relationships, especially with influential or powerful persons.
    • Mathematics. pertaining to a set for which no cover exists, consisting of two open sets whose intersections with the given set are disjoint and nonempty.
  • Installed
    • to place in position or connect for service or use:
      • to install a heating system;
      • to install software on a computer.
    • to establish in an office, position, or place:
      • to install oneself in new quarters.
    • to induct into an office or the like with ceremonies or formalities.
  • Linked
    • Digital Technology. to create links in or have links to a web page or electronic document:
      • The page is linked to my online store.
      • The essay links to three of my published articles.
  • Operative
    • operating, or exerting force, power, or influence.
    • having force; being in effect or operation:
      • laws operative in this city.
    • effective or efficacious.
    • engaged in, concerned with, or pertaining to work or productive activity.
    • significant; key:
      • The operative word in that sentence is “sometimes.”
  • hooked up
    • to seize, fasten, suspend from, pierce, or catch hold of and draw with or as if with a hook.

Example Sentences of the Words in Context


The English language is complicated and ever-changing. A lot can change over time and as words shift in the cultural landscape of American English in the United States and British English, so you can easily wonder if you have been spelling one word wrong or if it’s another word that has two different spellings with two words and a hyphen in the middle.