Throughout this work, we will denote forgetful functors that forget structure by ${\text{忘}}$, e.g. as in

\[ {\text{忘}}\colon \mathsf{Grp}\to \mathsf{Sets}. \]

The symbol ${\text{忘}}$, pronounced wasureru (see Item 1 of Remark 8.4.3.1.6 below), means to forget, and is a kanji found in the following words in Japanese and Chinese:

  1. 忘れる, transcribed as wasureru, meaning to forget.
  2. 忘却関手, transcribed as boukyaku kanshu, meaning forgetful functor.
  3. 忘记 or 忘記, transcribed as wàngjì, meaning to forget.
  4. 遗忘函子 or 遺忘函子, transcribed as yíwàng hánzǐ, meaning forgetful functor.


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