Meaning of RE in English

[re] n [ML, fr. the syllable sung to this note in a medieval hymn to St. John the Baptist] (14c): the 2d tone of the diatonic scale in solmization

[2]re prep [L, abl. of res thing--more at real] (1707): with regard to: in re

Merriam-Webster English vocab.      Английский словарь Merriam Webster.