Some manuals of style remain neutral on the subject. The Chicago Manual of Style states: “On the one hand, it is unacceptable to a great many reasonable readers to use the generic masculine pronoun (‘he’ in reference to no one in particular). On the other hand, it is unacceptable to a great many readers either to resort to nontraditional gimmicks to avoid the generic masculine (by using ‘he/she’ or ‘s/he.’ for example) or to use ‘they’ as a kind of singular pronoun.” (233) Those objecting to the generic masculine pronoun are described as “reasonable readers” while those objecting to the singular they remain unmodified by any such adjective. However, ‘he/she’ and singular they are described as nontraditional gimmicks. This stops short of an endorsement of any particular course of action.

Other style manuals explicitly reject the use of the singular they in grammar. According to the Publication Manual of the American Psychological Society, a pronoun must agree in both gender and number with the noun it replaces. The APA manual offers the following example as incorrect usage:
“ Neither the highest scorer nor the lowest scorer in the group had any doubt about their competence.[48] ”

The APA recommends using “he or she,” using “they” with a plural subject, or simply rewriting the sentence to avoid issues with gender or number.

The Purdue Online Writing Lab (OWL) also maintains that pronouns must agree in number, and that the singular they is incorrect usage.