I believe the right hand side of a comparison (i.e. the thing being compared to) can be termed a 'comparand'. Is there a word that can be used for the the left hand side of that equation? I.e. the thing that we're comparing?

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    "comparand" has no significant currency (it's not in OED). But if you're prepared to use it at all, I see no reason why it shouldn't be applied to the terms on either side of the "equals" sign (=) of an equation (or either side of other comparators, such as <, >=, GT, etc.). Commented Jun 5, 2017 at 15:05
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    @FumbleFingers Is correct as usual, both operands (<- note!) to a comparison are termed comparands, but for fun, if you wanted to coin a plausible-but-technically-incorrect term to distinguish one side from the other, you could pattern them after the pairs augend+addend, minuend-subtrahend, multiplicand*multiplier, dividend/divisor, and name them comparand<comparor. [cont'd]
    – Dan Bron
    Commented Jun 5, 2017 at 16:32
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    @Dan Bron: Not entirely correct. I knew as I wrote it that I was on shaky ground calling those things comparators, but operators had temporarily slipped my mind (besides which I really wanted to use a form reminiscent of comparand, even though my browser keeps doggedly underlining that one! :) Commented Jun 5, 2017 at 17:27
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    If you're talking about English grammar and semantics instead of mathematics, then the usual term is focus for the thing being held up for comparison, and baseline for the thing being used as a standard for comparison. Baseline propositions (or their predicates or anaphors) are what is introduced by than in comparative constructions; that is the only occurrence of than in English, and its presence identifies a construction as comparative. Commented Jun 5, 2017 at 18:25
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    @Ooker: In grammar, semantics, pragmatics, and linguistics generally. If this is a question about English and not mathematics, that is. Commented Jun 6, 2018 at 14:18

5 Answers 5


Most of the discussion relating to this subject is found in a computer science/programming context, where the "direction" or "non-commutative properties" of a comparison operation are more obvious. One of the expressions (the left-hand expression, for example) could call a function that would modify a variable included in and affecting the evaluation of the other expression, making the order of evaluation an important issue (this is true of other arithmetic operations too: see Word for the number being added-to OR subtracted-from another number on ELU, mentioning the use of lhs and rhs, https://math.stackexchange.com/questions/803844/word-for-the-number-being-added-to-or-subtracted-from-another-number on math.se for a one-off turned two-off of loperand and https://stackoverflow.com/questions/579421/often-used-seldom-defined-terms-lvalue on SO)

One option, very general to be sure, is to call the objects on both the right and the left comparison operands.

(from en.cppreference.com) (emphasis added):

Arithmetic comparison operators

If the operands have arithmetic or enumeration type (scoped or unscoped), usual arithmetic conversions are performed on both operands following the rules for arithmetic operators. The values are compared after conversions

And citing Joe Celko's SQL for Smarties (Fourth Edition),sciencedirect.com says (emphasis added):

The comparison operators are overloaded and work for , , and data types. They return a logical value of TRUE, FALSE, or UNKNOWN where the values TRUE and FALSE follow the usual rules, and UNKNOWN is always returned when one or both of the operands is a NULL.

If values that don't need evaluation are provided, the comparison operators don't care which end you start comparing at as long as you respect the operator (as FumbleFingers pointed out in a comment). That is, a < b could be read "a is less than b" or "b is greater than a".

Or in one word, comparands (if you don't mind wiktionary):

(linguistics, computing) A thing to which something is compared

Or arguments, calling out the right or left hand one, like at http://cs.union.edu/~striegnk/learn-prolog-now/html/node42.html (emphasis added):

Moreover, they force both their right-hand and left-hand arguments to be evaluated

Again, the comparison operator doesn't care where you start comparing; you would need some other way to indicate that one of the objects is the "benchmark", "standard" or "subject" (a few un-referenced suggestions from wordreference).

IBM calls them both "operands" and "comparands" at https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_71/rzase/sc092540262.htm (emphasis added):

If your arithmetic is a comparison (contains a relational operator), then the numeric expressions being compared—whether they are data items, arithmetic expressions, function references, or some combination of these—are really operands (comparands) in the context of the entire evaluation. This is also true of abbreviated comparisons; although one comparand might not explicitly appear, both are operands in the comparison. When you use expressions that contain comparisons in ILE COBOL, the expression is evaluated as floating-point if at least one of the comparands is, or resolves to, floating-point; otherwise, the expression is calculated as fixed-point.

For example, consider the following statement:

IF (A + B) = C or D = (E + F)

In the preceding example there are two comparisons, and therefore four comparands. If any of the four comparands is a floating-point value or resolves to a floating-point value, all arithmetic in the IF statement will be done in floating-point; otherwise all arithmetic will be done in fixed-point.

  • Off-topic: Incidentally, you could also consider the option of comparing without using comparison operators: techiedelight.com/…. The question would then become: "What to call the operand on the left hand of a logical operator?"
    – Conrado
    Commented May 2, 2020 at 2:04
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    Is this suggesting lhs in preference to LHS? It's hard to see which is more common, although you could check the standards for your favourite language.
    – Stuart F
    Commented Nov 18, 2023 at 12:21

Let A be the thing to be compared, and B the thing to compare, that is:

A is like B

then according to the structure mapping engine (SME), A is called source and B is called target.

SME maps knowledge from a source into a target.

Say we have a sentence: "The hydrogen atom is like our solar system". The "hydrogen atom" is the source, "solar system" is the target.

In the original paper of Gentner, A is called the base.

FYI: Analogy - Wikipedia

  • The link to the Gentner paper doesn't work. That aside, from your answer, I don't understand the relationship between a mapping of one set to another (for example) and a comparison. Would you mind explaining? I apologize if it's a dumb question -- I'm just trying to understand your answer. Commented May 2, 2020 at 1:03
  • No worry. I've updated the link. Say we have a sentence: "The hydrogen atom is like our solar system". The "hydrogen atom" is the source or base, "solar system" is the target
    – Ooker
    Commented May 2, 2020 at 9:56
  • I'm pretty sure you have it backwards. B is the source and the transfer goes right to left.
    – Phil Sweet
    Commented May 2, 2020 at 12:09

If "comparand" is that which is to be compared, then "comparator" would I guess be that which it is compared to.

I based that on "dividend" that which is to be divided, and "divisor" that which divides.

The word exists...

1.2 Something used as a standard for comparison.
‘even taking the most favourable comparator the company is about 20 per cent higher’

Note: comparand is not in OED

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    Why is OED more important than other dictionaries?
    – Ooker
    Commented Jun 6, 2018 at 14:26
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    Most math types would call them both "comparands".
    – Hot Licks
    Commented May 2, 2020 at 0:20
  • In many decades of doing mathematics (if that's what the OPs' question concerns), I have never encountered the term comparand. Also, in the physical sciences, a comparator is an instrument used to compare one thing, usually a physical object, to another or to a specified standard. See, for example, [precisioncalibration.com/2017/03/25/…. Commented May 2, 2020 at 0:41
  • On the positive side, a different meaning of comparator appears to have currency in the U.K. Cambridge defines comparator as an organization, activity, etc. that is used to judge the performance of another similar organization or activity. In the U.S., we would call such an organization, activity, etc. a benchmark or a standard. This jives with the definition you've referenced. Commented May 2, 2020 at 0:46
  • @Ooker OED is recognised by virtually all linguists as the sine qua non of English language dictionaries. It is the best researched and vetted. It may not respond as quickly as some others do to new usages which may be worthy of inclusion in the lexis (Wikipedia contains more headwords), and doesn't list senses in order of currency (being a historical dictionary), but its filters are the best. It is peerless in research presented on words actually included. As is the case with all other dictionaries, its treatment of grammar would be better left to dedicated works. Commented Nov 16, 2023 at 16:22

They are both from Latin.

Comparandum: "The thing to be compared"


Comparans: "the comparing thing"

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    Hello, 436. What are 'they'? Are your candidates actual words in the English lexis ... do they have reasonable currency? If they're just projections from Latin, with no currency, they're not acceptable as answers on ELU. Commented Oct 18, 2021 at 13:23
  • Perhaps this answer is arguing from Karl Popper, who used explicandum and explicans in an analogous sense. These appear to be relatively recent coinages, although older than Popper. Commented Oct 26, 2021 at 23:18
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    There are quite a few usable Latin phrases in academic English that people understand even if they are not in a dictionary and, therefore, technically not English. The fact is "comparans" answers the OP's questions better than any other substitute. Even if the ELU rejects it, that's the word I'd use.
    – user436436
    Commented Dec 22, 2021 at 17:14
  • Definiendum/definiens and explanandum/explanans are well established pairs of technical terms (which a fair number of of non-specialists may encounter in introductory-logic courses); anybody who is familiar with these terms is likely to 'get' the meaning of comparandum/comparans, even if they are not in a dictionary. This answer, however, appears to be a variation on what was posted before in the comments below the question, and that should have been acknowledged.
    – jsw29
    Commented Nov 16, 2023 at 17:36

You can also compare the unknown to the known.

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