After the Vulcans and Romulans split by just looking at one how can you tell the difference? For example on one of the episodes a guy looks at Spock and says he is a Vulcan but how does he know he's not a Romulan?

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    Which guy, and which episode would help. Until Balance of Terror, no-one in TOS knows what a Romulan looks like, even the Vulcans at that point don't know that the Romulans and the 'non-Surak accepting vulcans' are one and the same. Vulcans and Romulans look identical Sarek, and the Roumulan Commander both being played by Mark Leonard. Commented Dec 15, 2017 at 13:32
  • 5
    Cut 'em open and count the rings.
    – Valorum
    Commented Dec 15, 2017 at 15:44
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    No, wait, that's trees.
    – Valorum
    Commented Dec 15, 2017 at 15:45
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    Context. I can't tell apart a wolf from certain dog breeds (and neither can a lot of people or film makers wouldn't be able to get away with stuff), still I would never say to someone: nice wolf! If it's with a person, it is a dog. If it is with star fleet, Vulcan
    – Raditz_35
    Commented Dec 15, 2017 at 15:53
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    If they're shooting at you and mouthing off about how superior they are to you, they're probably Romulans.
    – Valorum
    Commented Aug 8, 2021 at 18:59

5 Answers 5



Prior to "Balance of Terror", most of the species in the Federation were only aware of one pointy eared, green blooded species. Therefore, any Romulan they met would instantly be a Vulcan in their eyes.

After "Balance of Terror", the majority of Romulans encountered were part of the Romulan Military (on board Romulan ships, wearing Romulan uniforms etc).

Similarly, Vulcans were generally encountered where one would expect to find a Vulcan (Federation or Vulcan starships, bases etc.)

Beyond that, there would be behavioral cues. For example, regarding Amabssador T'Pel:

The script for "Data's Day" ... says, "She is Vulcan, middle-aged, and has the cool, regal bearing common to her species."

Cool and regal are not Romulan traits by any stretch.

On some occasions, such as with Ambassador T'Pel/Sub Commander Selok, Vulcans and Romulans were able to pose as a member of the other species without altering their physical appearance.

  • Talok in the 22nd century
  • Selok in the 24th century
  • T'Paal in the 24th century

The only thing that these characters changed was their behavior, hairstyle and clothing so they would seem more Vulcan or Romulan as the situation required. Unlike Kirk, Picard, Data and Troi-no cosmetic surgery was necessary.

Let's not forget about Simon Tarses who was part Romulan but passed for Vulcan and was never questioned about it until the events of "The Drumhead".

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    Also, Spock in "Unification". Commented Aug 9, 2021 at 12:43

In TOS "The Paradise Syndrome" Spock studies the ancient writing of the Preservers and learns to read it:

SPOCK: You prescribed rest, Doctor. The symbols on the obelisk are not words. They are musical notes.
MCCOY: Musical notes? You mean it's nothing but a song?
SPOCK: In a way, yes. Other cultures, among them certain Vulcan offshoots, use musical notes as words. The tones correspond roughly to an alphabet.

So Spock knows of at least two Vulcan offshoot cultures that use musical notes as words, and at least one that doesn't. These three or more Vulcan offshoot cultures may be primitive ones protected by the Prime Directive and studied in secret or full fledged members of interstellar society that Humans and Vulcans sometimes met. Presumably these Vulcan offshoot people dress and behave differently than Vulcans and so can be told apart.

Furthermore, "Journey to Babel" indicates the natives of Rigel V have a similar physiology to Vulcans and possibly a similar appearance, and possibly are members of the same species.

SPOCK: Doctor.
MCCOY: I see it, Spock, but that was a Rigelian.
SPOCK: Rigelian physiology is very similar to Vulcan.
MCCOY: Similar is not good enough. It's still experimental.

Thus the statement in Geewhiz's answer that:

Prior to "Balance of Terror", most of the species in the Federation were only aware of one pointy eared, green blooded species. Therefore, any Romulan they met would instantly be a Vulcan in their eyes.

Should be only partially accurate in the interstellar civilization of TOS.

  • You're not wrong. However evidence points to those offshoot cultures not being part of interstellar society. We only ever see two pointy eared green blooded warp capable species (Romulans and Vulcans, 3 if you count Remans). Also, the cultures we do see are almost universally identified as Vulcan, Romulan or Reman-nobody ever looked at a Vulcan and thought it was Debrune for example. This would imply that the offshoots are pre warp, extinct or intentionally staying out of interstellar politics.
    – geewhiz
    Commented Dec 16, 2017 at 17:48
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    Addressing the quote about Rigellians. Physiology and Morphology should not be confused. Physiology is the study of HOW the body works not what it looks like. Physiologically, Romulans and Klingons share similarities that make them good donors for one another but nobody would mistake one for the other. I don't think a Rigellian has ever been shown on screen but until one is, we can't simply assume they look Vulcan.
    – geewhiz
    Commented Dec 16, 2017 at 17:51

While not canon, the book "My Enemy My Ally" by Diane Duane has the following quote from McCoy, which gives a physiological reason.

The quote is discussing a plot to invade a Romulan station with the aid of Romulans (matter of honor), and having the Rihannsu act as Vulcans with each boarding group:

"They won't think that for long, Spock," McCoy said. "Remember, Rihannsu and Vulcan culture have been diversing for thousands of years...and most of the subconscious cues buried in their respective kinesics, their 'body language,' will also now be very different. A Rihannsu would know you weren't one, if he looked long enough, not from any physical divergence- but just from a wrong 'feel.'"

So basically, while a Vulcan may outwardly look like a Romulan, there are ways of walking, acting, talking that are endemic to any culture, and if a person does not fit that, they give off a wrong vibe to people of the culture.

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    There was a TNG episode (Data's Day) in which a high-ranking Vulcan in Starfleet was revealed to be a long-time Romulan spy. Also, in "Unification", Spock was pretty much able to wander around without drawing attention to himself. There are also the "ridged-forehead" Rommies, but for all we know there may be Vulcans with the same trait and we've just never seen them. Commented Dec 15, 2017 at 14:51
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    @EmsleyWyatt yes, I did not include the TNG items. And there are spies that are trained to pass themselves in other cultures/races. That isn't available to most people, as evidenced by people that basically shout "tourist" just by their dress and/or actions.
    – JohnP
    Commented Dec 15, 2017 at 15:07

During TOS, Romulans and Vulcans appeared physically identical, and as noted in other answers, differentiation could only be done based on context, attire, or behavior.

TNG introduced a physical difference. As in TOS, Vulcans appear human except for eyebrows, ears, and skin tone; in addition to the Vulcan traits, TNG gave Romulans subtle ridges on the forehead above/between the eyebrows, giving them a slightly more menacing look and an obvious means to differentiate them. It's a more subtle case of the same thing that happened with Klingons between TOS and TNG.

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    While the forehead ridges seemed to be virtually omnipresent among Romulans in TNG onward, it should be noted that Spock lived and moved around on Romulus in TNG: "Unification" without any surgical or otherwise disguise, yet was not immediately recognized as a Vulcan. This seems like a pretty strong sign that not all Romulans have the forehead ridges (which is ultimately confirmed/retconned (depending on your view) in PIC where the ridges are said to be a regional trait. Commented Aug 8, 2021 at 19:43
  • @O.R.Mapper IIRC, he was tolerated, certainly, but I don't recall any scene in which he was clearly assumed to be a Romulan. If the ridges are a regional trait, why would all Romulans appearing in TNG have them? Out-of-universe, there was an artistic choice to give Romulans brow ridges which TNG discreetly (and I think wisely) chose not to explain in-canon. The choice to attempt an in-canon explanation in PIC is, I think, unfortunate.
    – Anthony X
    Commented Aug 8, 2021 at 23:43
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    "If the ridges are a regional trait, why would all Romulans appearing in TNG have them?" - well, that's what whoever made the artistic choice to change the makeup of an established species should probably have thought through. As it stands, we are left with the following evidence: (1) As established in TOS, (at least some) Romulans are visually indistinguishable from (at least some) Vulcans. They sport the common Vulcan/Romulan look with a smooth forehead. (2) From TNG onwards, we see Romulans with another makeup with forehead ridges. It appears side-by-side with the common Vulcan/Romulan ... Commented Aug 9, 2021 at 18:53
  • ... look with a smooth forehead, indicating that the new Romulan-only (?) makeup does not "override" or retcon the common Vulcan/Romulan look with a smooth forehead. Now, the only way how both (1) and (2) can hold is that there are some Romulans with forehead ridges and some with a smooth forehead. PIC finally confirmed this on screen. Don't get me wrong - I am not at all in favour of all the visual revisionism of post-ENT Trek, but in this particular case, PIC fixed a plothole created back in the days of TNG. Commented Aug 9, 2021 at 18:53

Hate to despoil the trek mythos, but in the The Next Generation sequel series before Discovery and Picard, the main visual difference was that the Romulan brow was more prominent. Watch the visual differences between enterprises T'pol and TNG's Romulan captain Picard plays chess with so often, Tomulok. Vulcans only look different to humans by the ears whilst the Romulan brow ridge would give them away in a flat second. And no I am by no means confusing them with Klingons; watch the videos where they talk about the makeup actors have had to have placed on them to play Romulans.

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    Can you be more specific about where the brow ridge appears? And can you then explain the cases where it does not?
    – DavidW
    Commented Jun 17, 2020 at 21:24
  • Also, in the TNG episode "First Contact" (not to be confused with the movie), there's a "proto-Vulcanoid" species which also has the Romulan prominent brow ridge. I have the feeling that if the show-runners could have gotten away with it, Vulcans would have had the brow ridge as well, in the same way that Klingons look very different from the TOS Klingons.
    – user888379
    Commented Jun 17, 2020 at 21:50
  • @user888379: That was rather "Who Watches the Watchers?" than "First Contact", right? Commented Aug 9, 2021 at 17:38
  • @O.R.Mapper You're quite right. Thanks for catching that. I wonder how many years ago "Who Watches the Watchers" turned into "First Contact" in my head :) ?
    – user888379
    Commented Aug 9, 2021 at 22:34

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