Double is to triple as halve is to ...?

"Divide by three" is the only way I know to say this but I'm looking for a single word, if one exists.

• Is there a verb that fits in the pattern: quarter, third, halve (divide), ???, double, triple, quadruple. . .? seems to imply it should be third, but I've never heard that verb usage. Dec 22, 2015 at 19:19
• Double is to triple as halve is to "cut into thirds." Dec 22, 2015 at 19:21
• Double is to triple as halve is to three fourths. Hah! I rock the SATs Dec 22, 2015 at 20:00
• You don't usually hear third used by itself like half. But I regularly hear a third or one third. For instance "I'll take a third of that za." That violates the single word restriction though. Dec 22, 2015 at 21:21
• But a half is obviously singular, as it's one or the other half in question. With thirds, you could have one or two thirds, hence having to generally speak about a third or one third. Dec 22, 2015 at 22:50

The OED defines third, verb, as such:

To divide (anything) into three equal parts; to reduce to one third of the number or bulk.

and it gives an example from 1874:

Such a course would have halved or thirded the number of our subscribers.

However, as choster pointed out in a comment, this seems to be rare.

I did an ngrams search which shows the relative changes in halved, thirded over time, and the usage of halved has increased while the usage of thirded has decreased. Similarly, the usage of thrice is also decreasing over time. This suggests to me that you should avoid using the word "thirded" despite it being a recognized usage.

Another answer provides the word "trisect". This word doesn't fit precisely in the collection "quartered, X, halved", but rather goes with "bisect, trisect, quadrisect". These words seem to me to be more technical in nature, used for geometry (e.g. Trisecting the Angle) or other mathematical or scientific contexts. Also, trisect can only be used for the sense "to cut into three equal parts" and not in the sense "to reduce to one third the size".

Tl;dr:

• If you want to fill the "quartered, halved, etc" group, use thirded.
• If you want language people actually use, just say "cut into thirds" or "divided into three" or something similar.
• If you need a current, single word, trisected is probably your best bet but it doesn't really fit the pattern nor satisfy all the meanings.
• I upvoted all three answers I see, but this is the best one. I upvote it harder. Dec 22, 2015 at 20:45
• "What man/ Thirds his own worth?" Two Noble Kinsmen, I, ii. Dec 23, 2015 at 10:29
• @DCShannon - Exactly the problem I always get. I want to be able to vote for "this answer is useful", and have a separate vote, one per question, which says "this answer is best". But only the OP gets those. :( No fair! Dec 23, 2015 at 14:03
• thirded makeths me thpbfeel like Daffy Duck Dec 23, 2015 at 20:55
• Interestingly, the present tense version of "third" as a verb has no results at all. I have no idea what to make of this. Dec 26, 2015 at 16:55
• to divide into three usually equal parts.

(M-W)

• Instead of a link-only answer and then filling the rest with garbage, you could provide a definition and citation. Just saying. Dec 22, 2015 at 19:29
• Exxept that would be: “double is to triple as bisect is to ________”
– Jim
Dec 22, 2015 at 20:15
• Halve and bisect are synonyms, so trisect works just fine. Dec 22, 2015 at 20:37
• @David: halve and bisect mean roughly the same thing, but they're not used the same way. You bisect an angle, or very rarely a path; you halve pretty much everything else. Dec 22, 2015 at 21:30
• I read trisect and it felt familiar (although in a way I would never use it) because of bisect, which is often used in programming. I then Googled, and somehow the word exists: quadrisect! I find "new" words every day... Dec 23, 2015 at 22:30

Halve means two things:

• to divide (something) into two equal parts: to divide (something) into halves
• to reduce (something) to one half of the original amount or size

For the first, trisect is a good option, but in my experience the second meaning is more common, as in The budget for our project was halved.

You cannot equally say: *The budget for our project was trisected, as that sounds as if it was split into three, and shared among three parties.

Your best bet for the second meaning is probably: The budget for our project was reduced to a third.

(Actually, trisect already sounds a bit mathematical and formal; it doesn't sound like something you'd say in casual conversation. Split in three is better there.)

I don't think there is a long-standing English word for dividing into three parts. Also, it looks like halve is from a word that originally meant divide without carrying the specific meaning of divide in two:

https://en.wiktionary.org/wiki/Appendix:Proto-Germanic/halbaz

I would also note that neither halve nor half appears to bear any relationship to words for two or three. By contrast twice and thrice are words for two and three with endings that signify use as an adverb.