| Kenneth G. Wilson (1923). The Columbia Guide to Standard American English. 1993. |
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| diagram (v.) |
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| In adding grammatical suffixes, some forms can use only one m, but two ms seem more frequent: both diagrammed and diagramed, diagramming and diagraming are Standard. Diagrammatic(al) and diagrammatically, however, are spelled only with two ms. See CONSONANTS (2). | 1 |
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| | | The Columbia Guide to Standard American English. Copyright © 1993 Columbia University Press. |
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