“10-4” – Its Meaning, Origin & Usage

Numerical code can sometimes move over into common use for the English language, and usually modern media has a lot to do with this, such as movies or tv shows. 

10-4 is one such numerical code. It’s part of the ten code which military and emergency services use, and essentially the code just means that you’ve heard and understood what has been conveyed to you.

Of course, when outside of these entities, 10-4 is just a way for other people to say they’ve heard you. But obviously, there’s a lot more we need to address here.

So, this helpful guide has everything you need to know about the phrase 10-4, including its origins and its uses. 

If you’re looking to know more – read on! 


It’s best that we first start by looking at the meaning of 10-4. Let’s examine further.

The Meaning Of 10-4 

As we mentioned earlier, the meaning of 10-4 comes from the usage of the “ten code” which is what military personnel, law enforcement and other emergency services may use. The reason for this code is to provide confirmation.

Because of the nature of their work, each person over radio communication must confirm that they have heard the previous correspondence and have acted on commands or advice. 

It’s arguable that 10-4 is a shortened phrase, because it’s often followed by the word copy. Using this word just reinforces the understanding that you have heard the previous command and you are relaying that you’ve acted on their advice etc. 

Away from the military and emergency services, truckers may use 10-4 as a way to tell their dispatch that they have heard them and will bear their advice in mind. On top of this, civilians might say 10-4 as a way to tell others they have heard them. 

Examples Of 10-4 

Now, let’s examine some examples of how 10-4 might be used. There could be the following scenarios:

John: Are you heading to the store, Bob?

Bob: 10-4 John, on the way right now. 

Operator: Do I have a cab to head over to Queens right now? 

Cab: 10-4 operator, car 65 on it as we speak. 

Operator: Squad 5, do you have the suspect detained?

Cop: 10-4 copy, we’ve got them in ‘cuffs. 

Operator: Truck 387, please head to drop-zone 4 first

Trucker: 10-4 copy, I’ll stop there on the way.

Other Ways To Say 10-4 

It’s a good idea that we also explore some of the other ways you could communicate the same thing without saying 10-4, so let’s look at some other potential scenarios: 

“Hey man, are you heading to the store?” 

“Yeah, I got you man – on the way right now!”. 

“John, have you managed to head to Queens yet?”

“Affirmative, I’m about 2 miles away”. 

“Officers, have you found the suspect?” 

“Roger, we have found the suspect and detained them.” 

Origins Of 10-4 

The origins of this phrase come from a  huge trend that started at some point in the 1970s and 1980s known as the CB radio. CB stands for citizens band and it was a useful tool for truckers, which arguably it still is. 

However, for people in the 1970s and the 1980s, they would have traced the origins back to huge movies at the time Cannonball Run and Smokey And The Bandit. In fact, it was around this era that many movies and TV shows would depict someone using a CB radio. 

Due to such popularity, people would get their own CB radio and communicate with other uses of it. As a result, users were driven to use the same language and communication codes as truckers or those on the movies and TV. 

Codes such as “what’s your 20?” which means “where are you?” became a normal place, and so too did 10-4.  Of course, with 10-4 in a CB context with others in order to socialize, it was primarily a way to confirm that you’ve heard what was previously said. 

The reason for this is because the bandwidth of CB radios are not especially strong and there were plenty of times where the frequency would cut out. As a result, many people using the CB radio would be unheard and would need to repeat. 

If this happened, a common response might be “sorry, DNC, did not copy, repeat, over”. Nowadays, CB radios are no longer as popular as they were, and are generally used for business purposes, if at all. 


10-4 is just a way for someone to confirm that they have heard something that someone has just said. It’s come a long way from CB radios to modern use!