Does the ゛ have any use?


Does the ゛ have any meaning in the hiragana alphabet?




I'm not 100% sure what you're asking here, but `゛` when used by itself
actually has a number of different usages.

Generally, `゛` ([Dakuten](https://en.wikipedia.org/wiki/Dakuten)) are not
written separately. For example, "か" "ka" becomes "が" "ga". If you didn't know
this, you should probably consult a reference on hiragana (and maybe also
katakana) as snailboat says.

However, there are a number of cases where `゛` is used by itself.

  1. The `゛` can add emphasis on some characters which Dakuten are usually not used on, as you can see at the question "[Encountered な with ten-ten](https://japanese.stackexchange.com/q/11898/796)".

  2. Half-width kana were used in the early days of Japanese computing, to allow Japanese characters to be displayed on the same grid as monospaced fonts of Latin characters. The tentens for half-width kana are displayed as a separate character. See also <https://en.wikipedia.org/wiki/Half-width_kana> for more information.

  3. Otherwise, the [Hiragana letter `ゔ` (vu)](http://www.fileformat.info/info/unicode/char/3094/index.htm) has often been written as `う゛` [apparently due to limited font/software support](http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q105064940). 

  4. Apparently you may also sometimes be asked to handwrite Dakuten into a separate box on some official forms. See also [On 原稿用紙, when are ゛ and ゜ (ten-ten and maru) supposed to occupy a square of their own?](https://japanese.stackexchange.com/questions/17390/on-%E5%8E%9F%E7%A8%BF%E7%94%A8%E7%B4%99-when-are-%E3%82%9B-and-%E3%82%9C-ten-ten-and-maru-supposed-to-occupy-a-square-of-thei)

In addition, this is a more technical usage, and you can almost certainly
ignore this if you aren't a computer programmer. Single characters with
Dakuten, for example "が", are separated into two characters (か and the
[COMBINING KATAKANA-HIRAGANA VOICED SOUND
MARK](http://www.fileformat.info/info/unicode/char/3099/index.htm)) when
normalized to the Canonical Decomposition, [Normalization Form D
(NFD)](http://unicode.org/reports/tr15/#Norm_Forms). NFD is used in (for
example) some databases as part of their collation algorithm, to make it
possible to determine whether any two strings are equivalent to each other.

