What is "soft sign"

n. The Cyrillic letter (l mul sc=Cyrl Ь)/(l mul sc=Cyrl ь), which in modern languages serves to denote a soft (palatalized) consonant.

The soft sign (Ь, ь, italics Ь, ь; Russian: мягкий знак ) also known as the front yer or front er, is a letter of the Cyrillic script. In Old Church Slavonic, it represented a short (or "reduced") front vowel. As with its companion, the back yer ‹ъ›, the vowel phoneme that it designated was later partly dropped and partly merged with other vowels.

In the modern Slavic Cyrillic writing systems (all East Slavic languages and Bulgarian and Church Slavic), it does not represent an individual sound but indicates palatalization of the preceding consonant.

It was also used in the Soviet Union in the Latinized Karelian alphabet, made official in 1931 and used until re- Cyrillicization of Karelian in 1937.