Hangul syllable Dyeon

It is a Korean syllable, not a word with one fixed meaning.

In some older Korean spellings, this syllable appears in a documented path from 뎐 through 젼 to modern 전. The initial ㄷ shifted toward ㅈ before ㅕ, a vowel with a y-like start; linguists call this sound change palatalization. It appears in late 16th century records and is clear in materials from the 18th century. Southern dialects show the change earlier, while some Seoul and northwestern texts keep older forms longer.

Hangul's earliest recorded appearance is dated to 1443; an explanatory book about the script followed in 1446. Hangul was designed to represent Korean speech more accessibly than Chinese-character writing, which many people could not use. 뎐 is one syllable built from Hangul letters, not a sign invented on its own.

What does it mean if someone sends 뎐?

Read it as Korean writing; context supplies the word.

In an old quotation, 뎐 may preserve an earlier spelling, so identify the whole word before translating it. In a modern message, it could be a deliberate old form, a fragment from a source, or a typo. If it stands alone, ask what word the sender intended.