It seems to be common to hear x = 3 sin(α) pronounced as

x equals to three sine alpha

I would read x = 3 sin(α) as "x equals three ...", and I believe this to be the correct pronunciation and hear it more commonly among mathematicians in formal settings and among well-read English-first-language speakers.

So what's origin of the "equals to" (mis?) pronunciation? How did it come to be so pervasive?

  • What is your evidence that this is common? I don't remember ever hearing it.
    – Colin Fine
    Commented Nov 23, 2021 at 14:59

2 Answers 2


There is a common and correct way of reading x = 3 sin(α)

x is equal to three sine alpha.

The use of "equal" as a verb to say "x equals..." is relatively modern. The word "equal" is still mostly used as an adjective except in mathematical contexts.

Given that a common colocation is "equal to", it is unsurprising that some people might treat the verb form as intransitive and say "x equals to ..." It is fairly harmless.

  • 1
    2 x 10 is equal to 10 + 10. But 2 x 10 equals 20.
    – Lambie
    Commented Nov 21, 2019 at 22:40
  • 1
    Yes, 2 × 10 equals 10 + 10, and 2 × 10 is equal to 20. The two ways of expressing are really quite synonymous.
    – James K
    Commented Nov 21, 2019 at 22:42
  • Oh interesting. Do you know when the verb equals started becoming common then?
    – minseong
    Commented Nov 21, 2019 at 22:56

In our language (Japanese), as Juhaz says at the comment line, there is no verb which is directly equivalent with the verb "equal".

For example, in your case, x=3 sin(α), we take as, (SOV case)


Here, 等しいis equal with English verb "equal", plus we need to insert a particle "と" in order for the sentence to make sense.

So naturally or not, we as learners may be intuitively thinking some particle, in English case, to, is needed to complete the sentence, again as Juhasz says.

But definitely in English it is "wrong".

  • 2
    This feels like a japanese SE answer...
    – minseong
    Commented Nov 21, 2019 at 22:55
  • @theonlygusti But you are saying "I hear a significant number of English-second-language speakers,", naturally the answer from the perspective of my own language could come. ( or other language speakers' )
    – user17814
    Commented Nov 21, 2019 at 23:03
  • 1
    @theonlygusti I think this is a fair answer to the question. Kentaro is simply using a concrete example from a non-English language to demonstrate the point. However, I'm kind of thinking there's a problem with the question. I'm not entirely sure we should be answering, "why is this mistake common?", or "what is the origin of this mistake?" Doesn't seem quite on-topic to me. Generally, addressing why something is wrong and giving the proper usage is more on-topic, not speculation about the origin.
    – Em.
    Commented Nov 22, 2019 at 2:12
  • @Em. did you delete all the topics on the OP? Some of them were p interesting...
    – minseong
    Commented Nov 22, 2019 at 2:45
  • @theonlygusti Do you mean comments? No, I did not delete them, but if there was an important point in there, the users can preserve them by posting an answer.
    – Em.
    Commented Nov 22, 2019 at 3:03

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