This is the 7721st most frequent French word.
sana
"Sana" is not a standard French word; it may be a name or a misspelling.
Here, 'Sa' is a possessive adjective meaning 'his' or 'her', depending on the gender and context of reference.
Sa sœur est très gentille.
His/her sister is very kind.
In this case, 'saine' is the feminine form of the adjective 'sain', meaning 'healthy', describing 'tête' which is a feminine noun.
Il faut avoir une tête saine pour une vie équilibrée.
It's necessary to have a healthy mind for a balanced life.
Here, 'Sana' is used as a proper noun, signifying a person and does not pertain to French grammar.