immersion

Etymology

From late Middle English, borrowed from Late Latin immersiō, immersiōnem (“dipping”).

noun

1. The act of immersing or the condition of being immersed.
   1. The total submerging of a person in water as an act of baptism.
      Jesus did not become known as a baptizer (cf. however John 3:26 and 4:1), but we can recognize the same ritual structure in his healing practice as in John's immersion. 2016, Risto Uro, Ritual and Christian Beginnings, Oxford University Press, page 98
   2. Deep engagement in something.
      Recognising and knowing how to understand visual imagery in relation to a narrative in picture books is primarily a matter of immersion in books within a specific culture. 2016, David Waugh, Sally Neaum, Rosemary Waugh, Children's Literature in Primary Schools, page 80
2. (Britain, Ireland, informal) An immersion heater.
3. (mathematics) A smooth map whose differential is everywhere injective, related to the mathematical concept of an embedding.
   Note that every embedding is an immersion, but the converse is not true. For an immersion to be an embedding, it must be one-to-one and the inverse must be continuous. 2006, William F. Basener, Topology and Its Applications, John Wiley & Sons, page 82
4. (astronomy) The disappearance of a celestial body, by passing either behind another, as in the occultation of a star, or into its shadow, as in the eclipse of a satellite.
   An occultation of a star by the moon provides two sharply defined observable phenomena: the disappearance of a star behind the disc of the moon (called its immersion), and its subsequent reappearance (or emersion). 2009, Steven Wepster, Between Theory and Observations, Springer Science, page 178
5. (education) A form of foreign-language teaching where the language is used intensively to teach other subjects to a student.
   Although numerous studies have reported the effectiveness of immersion programmes in developing relatively high levels of second language proficiency without any tradeoff of first language development or subject matter mastery, little is known of immersion education in Japan. 2001, Mary Goebel Noguchi, Sandra Fotos, Studies in Japanese Bilingualism, Multilingual Matters, page 272
6. One's suspension of disbelief while reading, playing a video game, etc. The experience of losing oneself in a fictional world.