A wiki page says

A prime meridian is the meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°.

which uses the phrase "is defined to be".

I found "is defined as" is more commonly used than "is defined to be" on ELL. Google Ngram might verify this.

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Are these two phrases interchangeable? If no. When to use which? Could someone please give a hint? Thanks in advance.

Archived: there was a typo in my previous search on ELL. The Google Ngram has alway been the same.

  • "defined to as" is nonsensical. That's why there were no results for it.
    – CJ Dennis
    Mar 20, 2020 at 23:46
  • I'm voting to close this question as off-topic because it is based on a misunderstanding.
    – CJ Dennis
    Mar 20, 2020 at 23:46

1 Answer 1


I believe your SE search had a typo in it. The phrase you want to be searching for is "defined as", not "defined to as". A quick ELL search for "defined as" brings up 370 results for me (roughly 5 times what "defined to be" returns), which is more consistent with the Google Ngram results.

The two phrases "defined as" and "defined to be" both mean the same thing and are pretty much interchangeable. As far as I know, the only reason to choose one or the other is a matter of stylistic preference.

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