RE

Re is a term with multiple meanings across fields and contexts. It can refer to a musical note, a chemical element symbol, a mathematical notation, a typographical prefix in correspondence, or a place name. Its meaning depends on the subject matter and usage.

In music, Re is the second note of the diatonic scale in solfège. In movable-Do systems it represents the second scale degree, while in fixed-Do systems it corresponds to the note D. It is part of the standard solfège syllables do, re, mi, fa, so, la, ti.

In chemistry, Re is the symbol for rhenium, a transition metal with the atomic number 75. Discovered in 1925 and named after the Rhine river, rhenium is a dense, silvery metal with one of the highest melting points. It is valued for use in high-temperature superalloys for jet engines, catalysts, electrical contacts, and other specialized applications.

In mathematics and computing, Re denotes the real part of a complex number, as in Re(z). In computing and text processing, RE is commonly an abbreviation for regular expressions, a syntax for pattern matching.

In language and communication, "Re:" (from Latin in re, meaning regarding) is used in letters and emails to indicate the subject matter or matter at hand. The term also appears in place names and abbreviations; for example, Île de Ré is a French island off the Atlantic coast, known for its beaches and fortifications.

Together, these senses show how "Re" spans disciplines from music and science to language and geography.