YouTube video (just click the link and it will automatically fast-forward to the right time mark for you which is located at about 1 minute 30 seconds)


Perhaps, this was the beginning of the cell as the unit of life. This cell membrane is thought to be only two large molecules thick. Nevertheless, it created an exterior and an interior and made possible the control of the environment inside the cell. The constant passage of water, nutrients and wastes keep conditions inside steady. These mechanisms allow a simple single-celled organism like amoeba to survive.

I don't understand why she left out the indefinite article that, to the best of my knowledge, absolutely must be there. We are talking about one amoeba, so it really should have been like an amoeba. Is there something I'm missing?

Post Scriptum:

And on top of that, it, of course, grammatically should be keepS conditions inside steady, not keep. Because the subject of the sentence is singular.

  • "Keep" is grammatically correct there. It talks about more than one thing.
    – Rucheer M
    Sep 21, 2015 at 9:38
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    No, the OP is correct. It's "This constant passage....keeps". Sep 21, 2015 at 9:41
  • Yes, you're right.
    – Rucheer M
    Sep 21, 2015 at 9:43
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    @AdityaAgarwal The head of the noun phrase is passage, a singular noun, so you'd expect the noun phrase to take singular agreement. Instead, we find keep, as though it's agreeing with the nearby noun wastes. This sort of error is called "proximity agreement" and is relatively common. The further the head noun is from the verb, the more likely it is.
    – user230
    Sep 21, 2015 at 11:33
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    That's right. "the passage of nutrients keeps" is correct. Sep 21, 2015 at 11:40

3 Answers 3


The English common name for single-celled organisms with pseudopods, "amoeba", sounds the same as the scientific name for one particular genus of amoebas, "Amoeba". Using the English common name for an organism in the singular usually requires an article, but it is normal to refer to a genus in the singular, without any article. This works when you are talking about characteristics of the entire genus. Check out the wikipedia page for Amoeba (genus) for more examples, including this:

Amoeba, like other unicellular eukaryotic organisms, reproduces asexually by mitosis and cytokinesis.

Added to address comments:

The transcript is from a spoken text, so there is no way to know if the speaker "intended" the word "amoeba" to be capital or italic. In writing, the standard for taxonomic nomenclature is that the genus name is capitalized, and the species name is not. The genus can stand alone, as in this case, but the species must have the genus with it. It is allowed to abbreviate the genus if it will still be clear from context. Also, when possible, the entire name is italicized. Any of the following would be correct:

  • Amoeba
  • Amoeba proteus
  • A. proteus

However, the following are technically incorrect:

  • amoeba (when italicized and used as a scientific name for the genus)
  • amoeba proteus
  • Amoeba Proteus
  • proteus
  • Proteus
  • This is the correct answer. The author did not forget to pluralize, the word amoeba refers to a singular category of creatures, the name of which category is "amoeba." This is not unique to biology, the same thing happens with musical groups all the time. When talking about the seminal British psychedelic band, we don't need to say "the Pink Floyd" we can just say "Pink Floyd."
    – barbecue
    Sep 22, 2015 at 0:12
  • @barbecue: So, then when used as a general reference to the species, I assume that the word "amoeba" should be capitalized if written, right? Sep 22, 2015 at 6:10
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    @barbecue: I think the situation is a little different from "Pink Floyd", which is a singular proper name, and cannot be used with an article, or to apply to the members of the group. To compare with another English band, "The Beatles", which is presented as a plural with an article, it is okay to say that John Lennon is "a member of The Beatles", or that he is "a Beatle". However, it is incorrect to say that Roger Waters is "*a Pink Floyd"; we must say he is "a member of Pink Floyd."
    – brendan
    Sep 22, 2015 at 8:40
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    @barbecue: The case for "Amoeba" is different. Although it is singular, we also have flexibility. We can label a diagram "Representative illustration of the structure of an Amoeba" or "Representative illustration of the structure of Amoeba" or "Representative illustration of the structure of a member of the genus Amoeba." All are correct, although I would prefer the second for a caption in a scientific text. The third construction would be better in a different context, such as "the organism was identified as a member of the genus Amoeba."
    – brendan
    Sep 22, 2015 at 8:41

The answer is that the writer failed to pluralize amoeba. So the "like" compares "organisms" (plural) to "amoeba" (singular). It should read

  • ...single-celled organisms like {amoebae/amoebas}.

If it's a formal scientific paper, I believe amoebae is the preferred plural. If it's not, one could use amoebas, or even (in AmE) amebas.

[edit: OP now clarified that transcript says "organism", not "organisms". So amoeba can be correct here. But we are not referring only to a single amoeba; we are referring to it as a representative of its kind; therefore, I would not say an amoeba. Instead:

  • ... a simple single-celled organism like the amoeba.
  • 1
    Actually, it was my bad. I transcribed it wrong. It should be "a simple single-celled organism". I fixed that now. Sep 21, 2015 at 9:58
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    Well, in that case, Ruchir was not off the mark after all. The writer is using singular amoeba to refer not to an individual, but to amoebae in general. This is commonly done, but one needs to use the, not an.! Sep 21, 2015 at 10:12
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    @BrianHitchcock: either "the" or "an" works here, in my opinion, although "the" is more idiomatic.
    – sumelic
    Sep 21, 2015 at 10:29
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    @CookieMonster: just that it's the better choice of word. As Brian Hitchcock says, since we are referring to a kind of "representative amoeba" rather than a specific single one, we can use the definite article here. This is a specialized use of the definite article that occurs with species names; you can also say "The giraffe is the tallest land mammal," talking about the species rather than any one specific giraffe.
    – sumelic
    Sep 21, 2015 at 10:37
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    Singular "Amoeba" as used in that sentence must have an article. As Sumelic and I have explained, the is more apt than an. Sep 21, 2015 at 11:14


In Microbiology, there are various simple, single-celled creatures like an amoeba. Probably, by referring amoeba without an indefinite article the narrator wants to refer to those 'amoebic' creatures in general.

In narration, at times, a narrator may use the singular form instead of plural by mistake. Therefore, we hear "like amoeba" though the narrator wants to convey "like amoebae".


As the OP has corrected, if it is for organism (singular), we can consider 'the amoeba' to indicate the entire species as pointed out by Brian Hitchcock.

  • 3
    There are many aggressive, sharp-eyed, short-tempered animals like cheetah in that jungle - if I don't want to be specific, in an informal speech, it seems okay to me. @snailboat
    – Maulik V
    Sep 21, 2015 at 9:52
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    I think treating amoeba as a game animal with a zero plural is highly unlikely.
    – user230
    Sep 21, 2015 at 9:56
  • Like @snailboat says, "amoeba" can only be singular. The plural is "amoebae" or "amoebas."
    – sumelic
    Sep 21, 2015 at 10:30
  • 1
    @MaulikV But "There are many animals like cow in that field" seems completely wrong. Sep 21, 2015 at 16:58
  • 1
    True, but cow is not a species or genus. "There are many animals like Bos Taurus in that field" would be fine.
    – barbecue
    Sep 22, 2015 at 0:03

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