One of the many tiny things that nanotechnologists have developed is a laboratory so small that a mere sliver of silicon can accommodate it. I don’t know what to admire more: this feat of engineering on the littlest imaginable scale or the succinct and graphic name they’ve coined for it, lab-on-a-chip (with lab-on-chip as a fairly common alternative).

But while the word is excellent, the plural is somewhat problematic. Opinions – or perhaps I should say intuitions – are divided between several options, and they nearly all make sense.

My own grammar gut tells me that lab-on-(a-)chip is a case like sister-in-law, tug-of-war and secretary-general. Unusually for English nouns, their main elements (known as heads) come first, which is why their plurals are sisters-in-law, tugs-of-war and secretaries-general. That strongly suggests that labs-on-(a-)chip would be the way to go. At just over 50%, this indeed is the most common form that a Google search turns up.

But hot on its heels, at 46%, is the alternative lab-on-(a-)chips. This seems odd at first sight, but on reflection, it has two important things going for it.

Firstly, there is the rather duh reason that adding a plural s at the end is how the overwhelming majority of English nouns form their plurals. That’s why you and I say sisters, tugs and secretaries, and it’s why some people also say sister-in-laws, tug-of-wars and secretary-generals. The latter set of plurals may pain many readers of this blog, but they’re by no means rare.

However, the main reason why the plural lab-on-(a-)chips occurs so frequently is probably a bit subtler and perhaps more commendable. When you meet your sister-in-law, she’s quite obviously much more like a sibling than a piece of legislation. Secretary-general is somewhat secretarial in nature and does not resemble a general. (Sepp Blatter, who reminds me of a general in a banana republic, is among the exceptions.) And while the word tug-of-war is a bit of a strange beast (to me anyway), the tug is usually more manifest than the war. So it’s always the head you notice most, not the add-on that specifies it (or the dependent, as it’s known).

But when you’re shown a lab-on-a-chip, you don’t see the lab so much – it’s the chip that stands out. As a result, it’s easy to assume that a lab-on-(a-)chip is a particular type of chip, along with the woodchip, the computer chip and the tortilla chip. In which case it goes without saying, almost without thinking, that the plural is formed by simply tacking on the usual s in the usual place: lab-on-(a-)chips.

This becomes even more self-evident when we consider an even newer nanotechnological device: the evolution-on-a-chip. Evolution is a process, not a concrete object, so an evolution-on-a-chip is first and foremost a chip. It takes a fine grammatically attuned mind such as yours to see that the head of the word, the part that would by rights claim the plural s, is evolution. The plural that most mortals will prefer is evolution-on-a-chips. I haven’t found instances yet, but wait for it.

A third, moderately frequent type of plural for lab-on-(a-)chip has not one, but two s’s: labs-on-chips. And if you ask me, there’s a lot to be said for that one too. After all, as soon as you have two of these labs, you also have two chips. With your in-laws, that’s different: no matter how many brothers, daughters, parents and other relatives by marriage you may have, the same law applies to all. Sisters-in-laws is plain silly. Labs-on-chips is good thinking.

Yet there is one plural that makes me shudder. Labs-on-a-chips is thankfully rare, and long may it remain so. Admittedly, it would be a legitimate plural for labs-on-a-chip, but since that singular is nearly non-existent, there’s no need to accept this grotesque plural.

One last observation. Some readers may feel that I’m dealing here with too minuscule an issue. I beg to disagree however. I’ve been blazing a trail into nanolinguistics.