Cyrillic Small Letter Yu

At a word's start, “you”; after a consonant, soft consonant plus “oo.”

Compare лю and лу: both end in an “oo” vowel, but лю marks a softened l. At a word's start, after a vowel, or after a separating sign such as ь, ю adds a y-like glide, so it spells “y + oo” with one letter. Early Cyrillic already used letters like ю for this y-plus-vowel sound; its earliest surviving manuscripts date to the 10th century. The Codex Suprasliensis, an early Cyrillic book of saints' lives and sermons, was copied at the end of the 10th or beginning of the 11th century.

How do I type ю?

On standard Ukrainian or Russian PC layouts, press the English period key.

Latin spellings such as yu, ju and iu are transliterations, not typing commands. Ukraine's official transliteration writes ю as Yu at the start of a word and iu elsewhere, so iu in a Ukrainian name may stand for this one Cyrillic letter.

Someone sent me ю by itself—what does it mean?

Ask about the surrounding word before reading a mood into it. A lone ю may be a cut-off word or a slip on the period key while the Cyrillic layout was on; the letter itself carries no feeling.