This is the 449th most frequent Finnish word.
sanna
"Sanna" is a Finnish female given name.
In this sentence, 'Sanna' is used as a proper noun, being the name of an individual.
Sanna on hyvä ystäväni.
Sanna is a good friend of mine.
Here, 'sanna' is used as a noun meaning 'sand' in a descriptive sense for the weather.
Ilmatieteen laitos ennustaa huomenna sannaista säätä.
The Meteorological Institute forecasts sandy weather for tomorrow.
In this context, 'sanna' is used to refer to 'sand' as a noun.