Concurrent vs Simultaneous – What’s the Difference?

These days, most of us are multitaskers, who handle more than one task at a time. When doing two things at the same time, do you say “Concurrent” or “Simultaneously”?

We want to find out if those two words are correct. And if they aren’t, what’s the difference between them?

Concurrent vs Simultaneous – What’s the Difference?

Both “Concurrent” and “Simultaneous” could be explained as meaning “at the same time”. However, there are some differences, because those words are similar but not identical in meaning. “Concurrent” is about two activities overlapping in duration. “Simultaneously” refers to things happening at the same instant, that share a connection.

concurrent vs simultaneous

Let’s look at some examples, before looking into each word separately:

  • Frank is showcasing his artwork in four concurrent art exhibitions.
  • Frank and Kenny are showcasing their artwork simultaneously at the museum’s art exhibition.

Read the sentences carefully. In the first sentence, Frank is showing his work at the same time in four different exhibitions. The word here is “Concurrent”, because the exhibitions are different events, in different venues, taking place at the same time.

Although they happen at the same time, they aren’t really connected.

In the second sentence, two men, Frank and Kenny, are showing their work at the same event, same venue, same time: therefore, the word here is “simultaneous”, because their exhibitions are, in a way, connected.


“Concurrent” relates to things that are happening or existing at the same time, but aren’t necessarily connected. The fact that they’re “Concurrent” things is a mere coincidence.

The definition in The Cambridge Dictionary corroborates this idea, expanding it a little, to give the example of a computer software that can be used at the same time by many people, who aren’t connected and aren’t performing the same job.

Let’s look at some examples:

  1. Sarah had to deal with both situations concurrently.
  2. The software was designed to handle hundreds of concurrent users.
  3. The computer was supposed to be running concurrently to the others.
  4. He will be serving two concurrent life sentences.
  5. Leonard was learning how to play guitar and piano concurrently.

In all sentences we see multiple things happening at the same time. However, they aren’t connected and don’t affect one another. That’s the idea behind “Concurrent”.


“Simultaneous” refers to things happening or being done at the same time that share some level of connection. “Simultaneous” things are more than a mere coincidence.

According to The Cambridge Dictionary, “Simultaneously” is the adverb that reaffirms that connection between things that exist or happen at the same time.

Here are some examples of “Simultaneous” in a sentence:

  1. The power outage was simultaneous in all of the houses on the block.
  2. He was simultaneously charming and annoying.
  3. Ashley had two simultaneous challenges to face.
  4. Fran was a great multitasker – meaning she could do many things simultaneously.
  5. Three simultaneous events took place at the venue, and they were all a success.

By the sentences, it’s possible to see that when an event is “Simultaneous”, it means they share some connection. In sentence 5, the common point was the venue. In sentence 1, it was the fact that all houses lost power at once (and likely got it back at one as well).

“Simultaneous” events aren’t random. There’s usually a reason for them to happen at the same time.

At the Same Time

“At the Same Time” is an expression that can interchange with “Concurrent” and “Simultaneous”, just making the statement a little less specific.

In The Cambridge Dictionary we find a definition that connects “At the Same Time” more with a conversation, where you need to add a new point or argument.

We’ll see examples of all cases below:

  1. Randy was excited to meet her, but at the same time anxious.
  2. Randy was simultaneously excited and anxious to meet her.
  1. The whole crowd screamed at the same time as the team scored a goal.
  2. The crowd screamed concurrently to the team, when they scored a goal.
  1. You expect too much of him – he can’t run the register and cook at the same time.
  2. He felt that she was kind but very mysterious at the same time.
  3. They both dropped their plates at the same time.

Sentences 1 and 2 interchange “At the Same Time” and “Simultaneous”. Sentences 3 and 4 interchange “At the Same Time” and “Concurrent”. The goal here was to show that those expressions can work the same way, with no loss of meaning.

What you must think about, as the speaker or writer, is which sentence would feel more idiomatic, or natural in the context of the message you’re attempting to convey. Also, you need to think about how polished you wish to sound.

“At the Same Time” is very simple and casual. “Concurrent” and “Simultaneous” can make a sentence sound more polished and educated. If you wish to impress someone, choosing one of those more complex words can help you achieve your goal more easily.

Which Is Used the Most?

Do people use “Concurrent”, “Simultaneous” or “At the Same Time” more often? We’ll take a look at the graph from Google Ngram Viewer below to search for the answer to this question.

simultaneous vs concurrent vs at the same time

“At the Same Time” is used with much more frequency. It’s quite impressive, but not exactly a surprise. “At the Same Time” is very colloquial, and easily used in all settings. We kind of expected it’d pop up more often.

“Concurrent” and ‘Simultaneous” are big words. At the same time they can make a sentence more polished and nice, they’re harder to use (and even to say, actually). Consequently, we see both words with roughly the same usage, way below “At the Same Time” on the graph.

Final Thoughts

It’s always good to have options that make your speech more interesting and clear. Use “Concurrently” when talking about things happening at the same time that share no connection with each other. “Simultaneous” should indicate things happening at the same time that are somehow connected to each other.