Letters or other characters saved as vector SVGs can be used for making proper font packages. This is done with some dedicated font editor in which you can import individual vector images and create a WOFF package that can be used by other users in their programs.
Found 2 different conversion types using the same filename extensions.
Conversion svg to woff type 1:
Convert from XML based scalable vector graphics format to Web Open Font Format package file.
On-line services software - convert svg to woff on web
A free web service for font conversion
File type (from-> to)
Convert from svg file format
XML based scalable vector graphics format
Web Open Font Format package file
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned svg to woff. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A tool for online conversion of fonts
Conversion svg to woff type 2:
Convert from SVG fonts format to Web Open Font Format package file.
Apple macOS / Mac OS X software - convert svg to woff on OS X
A tool for creating new fonts
Multiplatform software - convert svg to woff on any platform